x = apples and y = oranges
3x + 2y = 9.93...multiply by 2
2x + 3y = 9.82...multiply by -3
------------------
6x + 4y = 19.86 (result of multiplying by 2
-6x - 9y = - 29.46 (result of multiplying by -3)
-----------------add
-5y = - 9.6
y = -9.6 / -5
y = 1.92 <==== cost per kg for oranges
2x + 3y = 9.82
2x + 3(1.92) = 9.82
2x + 5.76 = 9.82
2x = 9.82 - 5.76
2x = 4.06
x = 4.06/2
x = 2.03 <== cost per kg per apples
========================
P = 2(L + W)
P = 30
L = 2W
30 = 2(2W + W)
30 = 2(3W)
30 = 6W
30/6 = W
5 = W <=== width is 5 cm
L = 2W
L = 2(5)
L = 10 <== length is 10 cm
=======================
x = first number and y = second number
4x + 3y = 15....multiply by 2
3x - 2y = 7...multiply by 3
-----------------
8x + 6y = 30 (result of multiplying by 2)
9x - 6y = 21 (result of multiplying by 3)
----------------add
17x = 51
x = 51/17
x = 3 <=== first number
3x - 2y = 7
3(3) - 2y = 7
9 - 2y = 7
-2y = 7 - 9
-2y = -2
y = -2/-2
y = 1 <=== second number
======================
x = sons age and y = fathers age
2x + y = 95
x + y = 70...multiply by -1
-------------
2x + y = 95
-x - y = -70 (result of multiplying by -1)
------------add
x = 25 <== sons age
2x + y = 95
2(25) + y = 95
50 + y = 95
y = 95 - 50
y = 45 <=== fathers age
=====================
sorry but I dont know the last one...never was good at those kinds of problems