Would you use count on or doubles to solve? why?

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years

Factor the polynomial by its greatest common monomial factor.

Find the volume of the solid bounded by the plane z=0 and the paraboloid z=1-x^2 –y^2