May I please have help. This is 7th-8th grade math.
30 POINTS

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

240 seventh graders and two-thirds of the students participate in after-school activities how many students participate in after-school activities

How is this equation completed? i cannot find any examples in the book.