Please explain how to do this problem and answer it please.

Consider circle h with a 3 centimeter radius. if the length of minor arc what is the measure of zrst?

Consider that lines b and c are parallel. what is the value of x? what is the measure of the smaller angle?

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! )