In the lab, Trey has two solutions that contain alcohol and is mixing them with each other. He uses 3 times as much Solution A as Solution B. Solution A is 17% alcohol and Solution B is 12% alcohol. How many milliliters of Solution B does he use, if the resulting mixture has 378 milliliters of pure alcohol?

Question

In the lab, Trey has two solutions that contain alcohol and is mixing them with each other. He uses 3 times as much Solution A as Solution B. Solution A is 17%  alcohol and Solution B is 12%  alcohol. How many milliliters of Solution B does he use, if the resulting mixture has 378 milliliters of pure alcohol?

anonymous · Answer

lets call the amount of solution B $x$ making the amount of solution A $3x$ (since it is three times as much)
then the amount of alcohol in solution A will be $.17\times 3x$ and the amount in solution B will be $.17x$

anonymous · Answer

oops i mean the amount in solution B will be $.12x$

anonymous · Answer

since the total is $378$ you can set 
$$.17\times 3x+.12\times x=378$$ and solve for $x$

anonymous · Answer

might be easier to get rid of the annoying decimals and solve 
$$17\times 3x+12\times x=37800$$