jika 7x +8y =-10 dan 6x + 2y=6,makA nilai dari 2x + 3y adalah....

pers I
6x + 2y = 6
24x + 8y = 24; dikali 4

eliminasi y pers I dan II
7x  +8y = -10
24x+8y = 24
___________ - 
- 17x = -34
x = 2

masuk ke persamaan I, substitusi x=2
6x + 2y = 6
6(2) + 2y = 6
12 + 2y = 6
2y = 6 - 12 = -2
2y = -2
y = -1

x = 2, y = -1
2x + 3y = 2(2) + 3(-1) 4 - 3 = 1

7x + 8y = -10 |x2
6x + 2y = 6 | x8

14x + 16 y =- 20
48x+ 16 y = 48
__________ _
-34x = -68
x = 2
y = -3
2x + 3y = 2.2 +3.-3
= 4-9
= -5