Maria bought seven boxes. A week later half of all her boxes were destroyed in a fire. There are now

Maria bought seven boxes. A week later half of all her boxes were destroyed in a fire. There are now only 22 boxes left. How many did she start with?

Take this in parts

1. Maria starts with b boxes.
2. She buys seven more. So she has b + 7 boxes
3. A week later, half of all her boxes are destroyed in a fire. Which means she's left with 1/2. (b + 7)/2
4. Now she has 22 boxes. So we set (b + 7)/2 = 22

(b + 7)/2 = 22

Cross multiply:
b + 7 = 22 * 2
b + 7 = 44

Typing this equation into our search engine and solving for b, we get:
b = 37