There were 630 T-shirts at a stall. ⁵₇ of them were without collars. T-shirts without collars were priced at $9 each. T-shirts with collars were priced at $12 each. The stall owner sold ²₃ of the T-shirts without collars and ⁷₉ of the T-shirts with collars. How much did he collect from all the T-shirts he sold?
Number of T-shirts = 7 u

7 u = 630

1 u = 630 ÷ 7 = 90

Number of T-shirts without collars
= 5 u
= 5 x 90
= 450

Number of T-shirts without collars sold 
= ²₃ x 450
= 300

Number of T-shirts with collars
= 2 u
= 2 x 90
= 180

Number of T-shirts with collars sold
= ⁷₉ x 180
= 140

Amount that the stall owner collected from the sale of the T-shirts without collars
= 300 x 9
= $2700

Amount that the stall owner collected from the sale of the T-shirts with collars
= 140 x 12
= $1680

Total amount that the stall owner collected from all the T-shirts he sold
= 2700 + 1680
= $4380

Answer(s): $4380