The usual price of a file sold at Shop E and F is $20. During a sale, a discount of 20% is given to every file sold at Shop E. At Shop F, a discount of 50% is given to the 5th file for every 5 files sold. How much cheaper would it be if Nicole buys 13 files from Shop E instead of Shop F?

	Shop E	Shop F
Price of 1 file	80%  $16	100% $20
Every 5th file		50% $10

Price of 1 file from Shop E in percentage
= 100% - 20%
= 80%

Price of 1 file from Shop E at 20% discount
= 80% x 20
= ⁸⁰₁₀₀ x 20 
= $16

Cost of 13 files from Shop E
= 13 x 16
= $208

Price of the 5th file from Shop F in percentage
= 100% - 50%
= 50%

Cost of 5th file at Shop F
= 50% x 20
= ⁵⁰₁₀₀ x 20 
= $10

Cost of 1 set of 5 files at Shop F
= 20 x 4 + 10
= $90

Number of sets of 5 for files at Shop F
= 13 ÷ 5
= 2 r 3

Cost of 2 sets of 5 files at Shop F
= 2 x 90
= $180

Cost of 3 files at Shop F
= 3 x 10
= $30

Cost of 13 files at Shop F
= 180 + 30
= $210

Amount cheaper if Nicole buys 13 files from Shop E instead of Shop F
= 210 - 208
= $2

Answer(s): $2