Solution for x=5-y and x+y=15

It might be no solution:

steps-

x=5-y

x+y=15

substitute the x (which is the top problem) into the second one.

(5-y) + y=15

cancel it out

(5-y) + y=15

-5. - 5

a negative plus a positive is gonna equal 0

-y+y=15-5

0=10

that is no solution ...