The usual price of a pencil sold at Shop J and K is $10. During a sale, a discount of 20% is given to every pencil sold at Shop J. At Shop K, a discount of 30% is given to the 7th pencil for every 7 pencils sold. How much cheaper would it be if Lynn buys 16 pencils from Shop J instead of Shop K?

	Shop J	Shop K
Price of 1 pencil	80%  $8	100% $10
Every 7th pencil		70% $7

Price of 1 pencil from Shop J in percentage
= 100% - 20%
= 80%

Price of 1 pencil from Shop J at 20% discount
= 80% x 10
= ⁸⁰₁₀₀ x 10 
= $8

Cost of 16 pencils from Shop J
= 16 x 8
= $128

Price of the 7th pencil from Shop K in percentage
= 100% - 30%
= 70%

Cost of 7th pencil at Shop K
= 70% x 10
= ⁷⁰₁₀₀ x 10 
= $7

Cost of 1 set of 7 pencils at Shop K
= 10 x 6 + 7
= $67

Number of sets of 7 for pencils at Shop K
= 16 ÷ 7
= 2 r 2

Cost of 2 sets of 7 pencils at Shop K
= 2 x 67
= $134

Cost of 2 pencils at Shop K
= 2 x 7
= $14

Cost of 16 pencils at Shop K
= 134 + 14
= $148

Amount cheaper if Lynn buys 16 pencils from Shop J instead of Shop K
= 148 - 128
= $20

Answer(s): $20