Question

how much cardboard would you need to construct a rectangular prism shaped box measuring 15 inches by 13 inches by 7 inches

Answer 1

We know that

[surface area]=2*[area of the base]+[perimeter of the base]*height

area of the base=15*13----> 195 in²

perimeter of the base=2*[15+13]----> 56 in
height=7 in
so
[surface area]=2*[195]+[56]*7-----> 782 in²

the answer is
782 in²