penyelesaian sistem persamaan -2x+3y=-7 dan 5x-2y=34 adalah(a,b+1).nilai 4a-b=...?

jawab

-2x + 3y = - 7 ..}kali 5
5x - 2y = 34.....}kali 2

-10 x + 15 y = - 35
10x     - 4y = 68....||(+)
11 y = 33
y = 3

-2x  + 3y = -  7
-2x  + 3(3) = - 7
-2x = -16
x = 8

(x,y)= (a , b+1)
a=x = 8
b+1 = y
b = y -1
b = 3-1
b = 2

nilai 4a - b = 4(8) -(2)
4a - b = 30