Algebra word problems

1. Sweder's hardware carries k yards of oak which sells for $3.75 a yard, and m yards of maple sells for $4.50 a yard. When a builder asks for a mixture of two kinds of wood, Sweder's sells him 50 yards at the price of $4.00 per yard. Find out the number of yards of each kind of wood the builder received. 

2.The price,u,of a laptop computer at Store A is $175 more than had price,k, of the same computer at Store B. The difference in price between the computer at store A and store B is $250. Determine the price of each computer at each store.

3.Illa's piggy bank contained only dimes and nickles. When she counted the money there was $12.85. If there were 143 more nickles than dimes, how many of each type of coin did Illa have in the piggy bank?