Question

n = x + y - n = 5
and part two
x = u + v = o

whats the answer?

Answer 1

Just substitute the value of x from second equation into first equation:
N = x + y - n = 5
N = u + v  + y - n = 5
N = 0 + y - n = 5

In short, N would be equal to y - n which is still equal to 5

Hope this helps!