Question

What is the y-coordinate of the solution to this system of equations?
5x-8y=1
3x+6y=-21

Answer 1

5x-8y=1...(1)
3x+6y=-21...(2)

(1)*3:
15x-24y=3...(3)

(2)*5:
15x+30y=-105...(2)

(3)-(2):
15x-24y-(15x+30y)=3-(-105)
15x-24y-15x-30y=108
-54y=108
y=-2