Question

Someone help please! I'm a confoosed bab:(

Answer 1

`\huge\boxed{A_(\triangle RST)=9units^2}`

Explanation:

(Look at the picture).

Calculate the area of the rectangle and subtract the areas of red triangles.

The formula of an area of a rectangle:

`A_{\boxed{\ }}=a\cdot b`

We have:

`a=5,\ b=4`

substitute:

`A_{\boxed{\ }}=5\cdot4=20`

The formula of an area of a triangle:

`A_\triangle=(a\cdot h)/(2)`

substitute:

`A_1=(3\cdot3)/(2)=(9)/(2)=4.5\\\\A_2=(2\cdot4)/(2)=(8)/(2)=4\\\\A_3=(5\cdot1)/(2)=(5)/(2)=2.5\\\\A_1+A_2+A_3=4.5+4+2.5=11`

Area of ΔRST:

`A_(\triangle RST)=A_{\boxed{\ }}-(A_1+A_2++A_3)`

substitute:

`A_(\triangle RST)=20-11=9`