The usual price of a marker sold at Shop Y and Z is $24. During a sale, a discount of 25% is given to every marker sold at Shop Y. At Shop Z, a discount of 50% is given to the 4th marker for every 4 markers sold. How much cheaper would it be if Natalie buys 15 markers from Shop Y instead of Shop Z?

	Shop Y	Shop Z
Price of 1 marker	75%  $18	100% $24
Every 4th marker		50% $12

Price of 1 marker from Shop Y in percentage
= 100% - 25%
= 75%

Price of 1 marker from Shop Y at 25% discount
= 75% x 24
= ⁷⁵₁₀₀ x 24 
= $18

Cost of 15 markers from Shop Y
= 15 x 18
= $270

Price of the 4th marker from Shop Z in percentage
= 100% - 50%
= 50%

Cost of 4th marker at Shop Z
= 50% x 24
= ⁵⁰₁₀₀ x 24 
= $12

Cost of 1 set of 4 markers at Shop Z
= 24 x 3 + 12
= $84

Number of sets of 4 for markers at Shop Z
= 15 ÷ 4
= 3 r 3

Cost of 3 sets of 4 markers at Shop Z
= 3 x 84
= $252

Cost of 3 markers at Shop Z
= 3 x 12
= $36

Cost of 15 markers at Shop Z
= 252 + 36
= $288

Amount cheaper if Natalie buys 15 markers from Shop Y instead of Shop Z
= 288 - 270
= $18

Answer(s): $18