Shouldn't x and y be equal to 72 ?
you can then make 2 equation, the one that you did
and x+y = 72
and solve them..
A chemist ran out of a 72 ml solution of 12% alcohol. All that is left in the lab is 8% alcohol and 20% alcohol. How many ml of 8% and 20% would be needed to make a 72 ml solution of 12%?
This is what I have so far.
.12 X 72=8.64
.08x + .2y=8.64
(100) .08x + .2y=8.64 (100)
8x + 20y= 864
Any help in solving it would be appreciated. I am at a dead end.