Algebra Word Problem Help
posted by Breanna .
Two wine merchants enter Paris, one of them with 64 casks of wine, the other with 20. Since they have not enough money to pay the custom duties, the first pays 5 casks of wine and 40 francs, and the second pays 2 casks of wine and receives 40 francs in change. What is the price of each cask of wine and the duty on it?

LEt P be the Price of each cast of wine, and D be the percent duty.
64P*D=5P+40
20P*D=2P40
multiply the second equation by 3.2
64PD=5P+40
64PD=6.4P128
subtract the second from the first.
0=1.4P+168
solve for P
then, go back to the original equation (either) and solve for D