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{7x + 7y = 35
{8x + 16y =56

Sagot :

Mlcparra16viz
So we have:
7x + 7y = 35
7(x + y) = 7(5)
x + y = 5 ... [1]

8x + 16 y =  56
8(x + 2y) = 8(7)
x + 2y = 7 ... [2]

[2] - [1] 
x + 2y = 7
-x -y = -5
    y = 2

We have:
x + y = 5
So:
x + 2 = 5
x = 3