Question

If x=2m-n and y=m+n, show that x-y=m-2n

Answer 1

x - y = (2m-n) - (m+n)

x - y = 2m-n - m - n

x - y = (2m - m) + (-n - n)

x - y = m - 2n

Don't forget to distribute the negative to each term inside (m+n)