A and b share a the cost in a ratio of 3:2 the cost is £85, how much does a pay?

85/5 = 17

17x3 = 51

17x2 = 34

51:34

A has to pay £51 (and B pays £34)

This is how you work it out: A:B

3:2

3+2=5, 85/5 = 17 (this is what you would have to pay if your part of the ratio was 1)

therefore, to find what A pays, you times the part 1 by 3 (as the ratio is 3:2)

17 x 3 = 51

(likewise, 17x2 = 34 which is what B has to pay)