Liam is selling 700 textbooks. He sold 50% of them at $10 each, 40% of the remainder at a discount of 40% and the rest at cost price. He made a profit of $2020. Find the cost price of a textbook.

Price	$10	$6	Cost Price
Percent	50%	50%
		20%	30%
Number	350	140	Not needed
Amount collected	$3500	$840	Not needed

Number of textbooks sold at $10
= 50% x 700
= ⁵⁰₁₀₀ x 700
= 350

Price after 40% discount
= 60% x 10
= ⁶⁰₁₀₀ x 10
= $6

Remaining textbooks
= 700 - 350
= 350

Number of textbooks sold at $6
= 40% x 350
= ⁴⁰₁₀₀ x 350
= 140

Number of textbooks sold at $10 or 40% discount
= 350 + 140
= 490

Total amount collected from the sale of 350 textbooks
= 350 x 10
= $3500

Total amount collected from the sale of the other 140 textbooks
= 140 x 6
= $840

Total amount collected from the sale of textbooks sold at $10 or 40% discount
= 3500 + 840
= $4340

Cost price of 490 textbooks
= 4340 - 2020
= $4900

Cost price of 1 textbook
= 4900 ÷ 490
= $10

Answer(s): $10