he paid 240 for a dozen tires (a dozen is 12)...so he paid 240/12 = 20 per tire
he sells 2 tires for as much as he paid for 3 tires...at 20 per tire, he paid (20 x 3) = 60.....so he sold 2 tires for 60...thats 30 per tire
so he is buying the tires at 20 a piece, but selling them at 30 a piece...so hes making a 10 dollar profit on each tire sold
so if he sold 12 tires...the profit would be (10 * 12) = 120
