The usual price of a notebook sold at Shop H and J is $20. During a sale, a discount of 25% is given to every notebook sold at Shop H. At Shop J, a discount of 40% is given to the 6th notebook for every 6 notebooks sold. How much cheaper would it be if Tiffany buys 15 notebooks from Shop H instead of Shop J?

	Shop H	Shop J
Price of 1 notebook	75%  $15	100% $20
Every 6th notebook		60% $12

Price of 1 notebook from Shop H in percentage
= 100% - 25%
= 75%

Price of 1 notebook from Shop H at 25% discount
= 75% x 20
= ⁷⁵₁₀₀ x 20 
= $15

Cost of 15 notebooks from Shop H
= 15 x 15
= $225

Price of the 6th notebook from Shop J in percentage
= 100% - 40%
= 60%

Cost of 6th notebook at Shop J
= 60% x 20
= ⁶⁰₁₀₀ x 20 
= $12

Cost of 1 set of 6 notebooks at Shop J
= 20 x 5 + 12
= $112

Number of sets of 6 for notebooks at Shop J
= 15 ÷ 6
= 2 r 3

Cost of 2 sets of 6 notebooks at Shop J
= 2 x 112
= $224

Cost of 3 notebooks at Shop J
= 3 x 12
= $36

Cost of 15 notebooks at Shop J
= 224 + 36
= $260

Amount cheaper if Tiffany buys 15 notebooks from Shop H instead of Shop J
= 260 - 225
= $35

Answer(s): $35