$1,200 in sales with 4% commission

What are the soultion(s) to the quadratic equation 40- x^2=0

Angela is buying a dress that is on sale for 20% off. if the original price of the dress is $40.00, how much money is angela saving on the dress? a. $0.80 b. $3.20 c. $32.00 d. $8.00

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'