50 POINTS AND BRAINLIEST. Pls help I've been doing the same problems for almost 3 hrs this is the last one I need

Iam in need of a tutor for my son in the northern ky area. can anybody me out

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! )

Find the volume of the wedge cut from the first octant by the cylinder z=12-3y^2 and the plane x+y=2.