[A] 2x + y = 18[B] x - y = 6Rearrange [A] to make y the subject 2x + y = 18minus 2x| y = 18 - 2xReplace the value y in [B] with the rearranged [A] x - (18 - 2x) = 6expand brackets| x - 18 + 2x = 6 simplify| 3x - 18 = 6 add 18| 3x = 24 divide by 3| x = 8Replace the value x in [B] Then rearrange to give y. 8 - y = 6 Minus 6| 2 - y = 0 Minus 2| - y = - 2Multiply by -1| y = 2To check that the values you have found for x and y are correct, plug the values in to equation [A] 2x + y = 18 2(8) + 2 = 16 + 2 = 18The answer is correct!