Tina baked 280 cookies. She gave 70 cookies to Celine and some cookies to Ben. She had 3/7 of the total cookies left.
(a) How many cookies did she have left?
(b) What fraction of the total cookies did she give to Ben?
number of cookies given to Ben --- x
cokkies left = 280 - 70 - x
210 - x = (3/7)(280)
-x = -90
x = 90