Answer:
18
Explanation:
(Note: I'm assuming that "starts out with" refers to the count before buying the four boxes)
Let x be the number of boxes Emily starts out with.
(x + 4) / 2 = 11
+
= 11
+ 2 = 11
We multiply both sides by 2 to eliminate the fraction.
x + 4 = 22
x = 22 - 4
x = 18