Answer part b and part c and explain step by step

Part B
Divide 63 by 3 to get 21, the price of one shirt.
Divide 21 by 7 to get 3, 10% of the original price.
Multiply 3 by 10 to get 30, the original price of one shirt.
$30

Part C
Divide 40 by 10 to get 4, 10% of original price 
Multiply 4 by 3 to get 12, 30% of the original price 
subtract 12 from 40 to get 28, the price after discount 
Divide 28 by 10 to get 2.8, the second 10% discount.
Subtract 2.8 from 28 to get 25.2, the final price.
$25.20