My little brother needs help and tbh I forgot all abt this

Acomputer store bought a program at a cost of $10 and sold it for $13. find the percent markup

The lengths of all sides of a triangle are integers when measured in decimeters. one of the sides has length of 1 dm and another of 3 dm. find the perimeter of the triangle.'

If f(x)=x+7 and g(x)=1/x what is (fog)(x)