What does y is a third as much as x

Which of the following transformations will always produce a congruent figure?

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! )

Given: δabc, m∠1=m∠2, d∈ ac bd = dc m∠bdc = 100º find: m∠a m∠b, m∠c