Erin and Evan had an equal number of baseball cards. After Erin gave away 37 baseball cards and Evan gave away 57 baseball cards, Erin had 2 times as many baseball cards as Evan. How many baseball cards did each have at first?
Since both started with the same number, let this = E
So
(E - 37) = 2 ( E - 57) simplify
E - 37 = 2E - 114
114 - 37 = 2E - E
77 = E
Each started with 77
+313 
