Question 100212
Let x=number of liters of white grape juice that needs to be added

(1)  The pure alcohol in the 2 liters of 12% alcohol is (0.12*2).
(2)  The pure alcohol in the white grape juice is (0).
(3)  The pure alcohol in the final mixture is (0.10(2+x))

Now we know that (1)+(2)=(3).  So our equation to solve is:

0.12*2=0.10(2+x)  get rid of parens and simplify
0.24=0.20+0.10x  subtract 0.20 from both sides

0.24-0.20=0.10x  collect like terms

0.04=0.10x  divide both sides by 0.10

x=0.4 liter---number of liters of white grape juice that needs to be added

CK

0.12*2=0.10*2.4
0.24=0.24


Hope this helps---ptaylor