You need to set it up as a fraction and make the fractions equal each other. 2/3 (2 of their books for 3 of yours) x/18 (x amount of their books for 18 of yours) (2/3)=(x/18) multiply both sides by 18 and you get 36/3 which reduces to 12
I think the question is asking for the cost (C) when we already know that the sell price (S) is $24 So C+M=S C+0.45C=24 1.45C=24 C=16.5516 And the answer is $16 and 55 cents
