Answer:
[tex](\frac{1}{2} b)+7[/tex]
Step-by-step explanation:
b= number of boxes she started with
We know that half of her boxes were destroyed in a fire, so we can represent that as [tex](\frac{1}{2} b)[/tex] , because she'll now have 1/2 of her boxes.
She then buys seven more, so we can add 7 to the equation, [tex](\frac{1}{2} b)+7[/tex].