Question 320219
7x+8y=36 ----------- (1)

x=60-8y ------------(2)

(2) gives an equation for x and hence we can substitute this value in place of x in (1)

So (1) becomes 7(60 - 8y) + 8y = 36 which is an equation in one variable. 

Simplifying, 7X60 - 7X8y +8y = 36

             420 - 56y + 8y =36
                   -48y =36 - 420
                   -48y = -384
                      y = -384/-48
                i.e   y = 8

So x = 60 - 8X8 (putting y=8 in (2))

   x = 60 - 64 = -4

Hence x = -4 and y = 8 is the required solution