Answer:
225
Step-by-step explanation:
Mary = 3x (3 times Carey)
Carey = x
Barry = x/2 (Because Carey read twice as many as Barry, it means he read half the amount Carey did)
3x + x + x/2 = 405
4x + x/2 = 405
8x/2 + x/2 (treat these as fractions) = 405
9x/2 = 405
9x = 810 (cross multiply)
x = 90
Mary = 3(90) 270
Carey = 90
Barry = 90/2 45
Mary - Barry
270 - 45 = 225
Hope this helps! :)
