Explanation:
Hello!
Part A
Peter can use the fact that 10% of 87 is 8.70 to find the amount he would save because 40% is just 4 times bigger than 10% so he can take 8.70 from to total of the coat 4 times to find out how much it cost.
Part B
Using the same method we know that 10% of 64 is 6.40 so we subtract that from the price of the coat 4 times to find out how much it cost
64 - 6.40 = 57.6
57.6 - 6.40 = 51.2
51.2 - 6.40 = 44.8
44.8 - 6.40 - 38.4
The price of the coat is $38.4
Hope this helps!