If x-y+z=10 and -x+y=3 what is the value of z?

A) 13
B) 7
c) 10/3
D) -7
E) -13

–x + y = 3 can be rewritten: –(x – y) = 3. That means that x – y = –3.

So x – y + z = 10 can be rewritten: –3 + z = 10. That means z = 13.