Hey i was looking for help on these problems; how would i go about finding the solutions to them both?

1.If a storage tank is holding 450 liters when it is three quarters full, how much will it contain when it is two thirds full?.

And

2.three people P,Q and R contribute to a fund. P provides 3/5 of the total, Q provides 2/3 of the remainder and R provides £8. determine a) the total of the fund. b)the contributions of P and Q.

Thanks