PLEASE HELP! I WILL GET A ZERO!!

Solve 5 tan x = 5√(3) for 0° ≤ x ≤ 180°. a. 60° b. 150° c. 30° d. 120°

In triangle abc, the length of side ab is 12 cm, the length of side bc is 5 cm, and the length of side ca is 9 cm. find the measure of angle a using the law of cosines.

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )