A local sporting goods manager gave each member of a basketball team a coupon for 20% off the regular price of one pair of basketball shoes.

Part A:
Tonya selected a pair of shoes for the regular price of $80. How much money will she save by using the 20% off coupon? Justify your answer using equations, models, and/or words to explain your mathematical reasoning.

Part B:
Katie selected a pair of shoes for the regular price of $120. After the 20% off discount is applied, what will be the discounted cost of the shoes (before tax)? Justify your answer using equations, models, and/or words to explain your mathematical reasoning.