1.) jika penyelesaian sistem persamaan 2x-3y=7 dan 3x+2y=4 adalahx=a dan y=b, maka nilai a-b= 2.) jika 3x-y=15

1) 2x - 3y = 7 |×2
3x + 2y = 4 |×3
maka
4x - 6y = 14
9x + 6y = 12
------------------(+)
13x = 26
x = 2
disubstitusi ke pers
2x - 3y = 7
2(2) - 3y = 7
4 - 3y = 7
- 3y = 7 - 4
- 3y = 3
y = - 1
jadi
x = a = 2
y = b = - 1
nilai a - b = 2 - ( - 1) = 2 + 1 = 3

2) 3x - y = 15
x + 3y = 3 |×3
maka
3x - y = 15
3x + 9y = 9
----------------(-)
- 10y = 6
y = - 6/10
y = - 3/5
• 3x - y = 15 |×3
x + 3y = 3
maka
9x - 3y = 45
x + 3y = 3
------------------(+)
10x = 48
x = 48/10
x = 24/5
nilai x - 2y
= 24/5 - 2(-3/5)
= 24/5 + 6/5
= 30/5
= 6