Nomor 1 caranya bagaimana.

2x - 5y = - 16 |×5
5x + 2y = - 11 |×2

10x - 25y = - 80
10x + 4y = - 22
------------------------(-)
- 29y = - 58
y = 2

2x - 5y = - 16
2x - 5(2) = - 16
2x - 10 = - 16
2x = - 16 + 10
2x = - 6
x = - 3

7x - 8y
= 7(-3) - 8(2)
= - 21 - 16
= - 37 (A)