Medium
What should be subtracted from (7x - 8y) to get (x + y + z)?
Explanation
Explanation
We need K such that (7x - 8y) - K = x + y + z. Rearranging, K = (7x - 8y) - (x + y + z) = 7x - 8y - x - y - z = 6x - 9y - z.
PRO TIP
Re-check your working by substituting the answer back into the original question.