Explanation:
![\large\underline{\sf{Solution-}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/auxvkffb37ppkivojcb9qg05yjvnvge1dw.png)
Given that,
- ABCD is a square of side x cm
- EFGH is a square of side y cm
Further given that,
- Sum of all sides = 52 cm
It means
- Perimeter of square ABCD + Perimeter of square EFGH is 52 cm
We know,
![\purple{\rm :\longmapsto\:\boxed{\tt{ Perimeter_([square]) \: = \: 4 * side \: }}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/t72zrojh35ssamebkio7ivi02kmshjiijq.png)
So, using this, we have
![\rm :\longmapsto\:4x + 4y = 52](https://img.qammunity.org/2022/formulas/mathematics/high-school/znn7uvlj0m26ufw21ejrmyxv52nlrp5prc.png)
![\rm :\longmapsto\:4(x + y) = 52](https://img.qammunity.org/2022/formulas/mathematics/high-school/ityvblv00q0khhtgn2chsiovynbrwyahdz.png)
![\rm\implies \:\boxed{\tt{ x + y = 13}} - - - - (1)](https://img.qammunity.org/2022/formulas/mathematics/high-school/p4rhcvg1xgi7136lqht1lfxke0hxtiahwr.png)
Now, Further given that,
If square EFGH is cutting out from square ABCD, the area of remaining part is 91 square cm.
It means
![\rm :\longmapsto\:Area_([ABCD]) - Area_([EFGH]) = 91](https://img.qammunity.org/2022/formulas/mathematics/high-school/ci52mkj1j8nxflse6zxbm6pytprwfg9106.png)
We know,
![\purple{\rm :\longmapsto\:\boxed{\tt{ Area_([square]) = 4 * side}}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/dzeu9ff9yqwpifk8gqo1ez84p52hgmkzya.png)
So, using this, we get
![\rm :\longmapsto\: {x}^(2) - {y}^(2) = 91](https://img.qammunity.org/2022/formulas/mathematics/high-school/z8o7dlf95wrkvlnadp1n8fjnfi695qf76v.png)
can be further rewritten as using algebraic Identity,
![\rm :\longmapsto\:(x + y)(x - y) = 91](https://img.qammunity.org/2022/formulas/mathematics/high-school/wzu8r8omhij8m9ionlss9zzvz7mb2c91ht.png)
![\rm :\longmapsto\:13(x - y) = 91](https://img.qammunity.org/2022/formulas/mathematics/high-school/pqscalgsx0a8g9so7s2o7bfmmps17lcy7c.png)
![\red{ \bigg\{ \sf \: \because \: using \: equation \: (1) \bigg\}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/mgn3gna37h7me2zse8lz3gh4bvhkxxqzkc.png)
![\rm\implies \:\boxed{\tt{ x - y = 7}} - - - - (2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/nl85k6ls9wu45px7udbbcr179p5j762t84.png)
On adding equation (1) and (2), we get
![\rm :\longmapsto\:2x = 13 + 7](https://img.qammunity.org/2022/formulas/mathematics/high-school/f1o3hcq52jt7g5ldkm06yp4qatozsoazqv.png)
![\rm :\longmapsto\:2x = 20](https://img.qammunity.org/2022/formulas/mathematics/high-school/amjxe500od2nob9m3vwpb873qbpszyq1uo.png)
![\rm\implies \:\boxed{ \: \bf \: \: x \: = \: 10 \:cm \: \: }](https://img.qammunity.org/2022/formulas/mathematics/high-school/6tjpaik9xcxvk9flczom2y7lu1g6xjrceu.png)
On substituting the value of x in equation (1), we have
![\rm :\longmapsto\:10 + y = 13](https://img.qammunity.org/2022/formulas/mathematics/high-school/xkbqp9ktb6x7t9hunbl04vj7w4ub6q3048.png)
![\rm :\longmapsto\:y = 13 - 10](https://img.qammunity.org/2022/formulas/mathematics/high-school/2opimptkgylr846ky51wa8nqyy18nyz5mc.png)
![\rm\implies \:\boxed{ \: \bf \: \: y \: = \: 3 \:cm \: \: }](https://img.qammunity.org/2022/formulas/mathematics/high-school/dxwml1ctwb43rirxo2sz4cmu68b99ml1zu.png)
So,
![\rm\implies \:\boxed{Side_([square \: EFGH]) = y \: = 3 \: cm}](https://img.qammunity.org/2022/formulas/mathematics/high-school/haqqrtp8fnl72c0bygpn869czyzyy73eob.png)
and
![\rm\implies \:\boxed{Side_([square \: ABCD]) = x \: = 10 \: cm}](https://img.qammunity.org/2022/formulas/mathematics/high-school/kerpuu96dhb08cwi1o1rqe0i100oh0vfez.png)
Also,
![\rm :\longmapsto\:\boxed{Area_([square \: ABCD]) = {10}^(2) = 100 \: {cm}^(2) }](https://img.qammunity.org/2022/formulas/mathematics/high-school/d2xs9idajvafx5lycfx8gsmifjetrbmym5.png)
![\rm :\longmapsto\:\boxed{Area_([squareEFGH] )\: = {3}^(2) = 9 \: {cm}^(2) }](https://img.qammunity.org/2022/formulas/mathematics/high-school/gqr4h05mmika9ddjztj8qnt5e39qq5e4ok.png)
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![\begin{gathered}\begin{gathered}\boxed{\begin {array}{cc}\\ \dag\quad \Large\underline{\bf Formulas\:of\:Areas:-}\\ \\ \star\sf Square=(side)^2\\ \\ \star\sf Rectangle=Length* Breadth \\\\ \star\sf Triangle=(1)/(2)* Breadth* Height \\\\ \star \sf Scalene\triangle=\sqrt {s (s-a)(s-b)(s-c)}\\ \\ \star \sf Rhombus =\frac {1}{2}* d_1* d_2 \\\\ \star\sf Rhombus =\:\frac {1}{2}d\sqrt {4a^2-d^2}\\ \\ \star\sf Parallelogram =Breadth* Height\\\\ \star\sf Trapezium =\frac {1}{2}(a+b)* Height \\ \\ \star\sf Equilateral\:Triangle=\frac {√(3)}{4}(side)^2\end {array}}\end{gathered}\end{gathered}](https://img.qammunity.org/2022/formulas/mathematics/high-school/yt51y9m5jxn5abud0nufb2ancebnmqr9p5.png)