How do you solve for x when x squared = 9?

45% of the trees in a park are apple trees. there are 27 apple trees in the park. how many trees are in the park in all?

Find the domain of the following expression: 1/(√x)-2

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