Answer:
Here you go
Step-by-step explanation:
Hope this helps :)
I believe the answer is 8.
problem 1 2x+5y= 0
×=-1/2-5/2y
problem 2 y=1 3/7y y=-1.428571
7y=-10
problem 3 x=-7
problem 4 x-y=20
x=-20