Can someone please help me with this geometry please?

Find the distance between (0,5) & (-4,2)

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! )

Which shows a reasonable estimation for 124% of 42 using the distributive property?