My teacher gave me a sheet of this and no instructions:

1. 5x+2y=10

-5x+7y=8

I don't know what I am suppose to do.

Probably wants you to find what numbers will work for x and y in both equations

add the two equations together

5x-5x+2y+7y=10+8

9y=18

divide both sdies by 9

y=2

subsitute into first equation

5x+2 (2) = 10

5x+4=10

subtract 4 from both sides

5x=6

divide both sdies by 5

x=6/5

so the asnwer is x=6/5 and y=2