algebra
posted by Holly .
Can someone PLEASE explain how to do this to me? Thank you so much!
Ten gallons of a 30% acid mixture is obtained by mixing a 50% solution (X) with 20% solution (Y). Write an equation for the 10 gallon mixture. What is the acid concentration, in gallons, of the final mixture? Write an equation for the acid concentration.

x+y=10  equation #1
.5x + .2y = .3(10)  equation #2