If s and t are integers greater than 1 and each is a factor of the integer n, which of the following must be a factor of n st ?

How do you write a paragraph proof to prove that the corresponding angles shown are congruent

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! )

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b