Answer:
Derek is currently 18 and Sarah is 8
Explanation:
20=(x-2)
-2 because it was 2 years ago
20=(x-2) + (2x-2)
2x because Derek is twice as old as Sarah
20=(x-2) + (2x-2) can be changed to
20= 3x - 4 when you combine like terms.
24 = 3x you divide by 3 and you get 8=x
You plug in the number and you get the answer
20=(8-2) + (2*8 - 2) which can be transferred to
20= 6 + 14