Let b represent the starting number of boxes. Then, after her purchase of 7 more boxes, Marla had x+7 boxes, which constitute half of the starting number:
(1/2)(x+7) = 22, or x+7 = 44. Thus, x = 37.
Marla started with 37 boxes.
She purchased 7 more, bringing her count to 44 boxes.
She lost half of these 44 boxes, or 22 boxes, in the fire.
Marla started with 37 boxes.
