Question 706248
Let g = amount of gallons of the 60% alcohol to add.
40% is target concentration.


{{{(g60+60*14)/(g+60)=40}}},(do not become confused about what the "60"s are counting while setting the initial equation.)


{{{60g+60*14=40(g+60)}}}
3g+3*14=2(g+60)
3g+3*14=2g+120
g+42=120
g=120-42=7
{{{g=7}}} gallons of the 60% alcohol