Me. this was my study page but this was hard.

Given that abcd is a rhombus, what is the value of x?

If value of cos330° is √3/2 then find tan165°.

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! )