A different approach:

Alcohol in soln1 = 3/4 and in soln2 = 2/5

Using Alligation:

3/4--------?--2/5

4 : 1

So the resultant ratio (the ?) is at a 1/5th distance from 3/4 (or conversely at a 4/5th distance from 2/5.

3/4 - 2/5 = 7/20

Now, calculating 1/5th of 7/20 and subtracting it from 3/4

(3/4) - (1*5)/(7*20)

= 75/100 - 7/100

= 68/100

= 68%

This approach is not quite advisable in this particular problem unless one is instinctive wrt alligation, but definitely awfully handy in other scenarios. This is just to enlighten people towards proper understanding of

Alligation _________________

In a Normal Distribution, only the Average 'Stand Out'