X = amount of the 18% solution
y = amount of the 40% solution
we know the 18% solution has only 18% of alcohol, the rest is maybe water or something, now, how many liters is 18%? well, 18% of anything is just (18/100) * anything, so, 18% of x is just (18/100) *x or 0.18x, and that's how many liters are there.
likewise, how many liters are there in the 40% solution? well, (40/100) * y, or 0.4y, that many.
we know the mixture has to yield 10 liters at 20% alcohol, how many liters of only alcohol is that? well, (20/100) * 10, or 2 liters.


how much of the 40% solution? well y = 10 - x
In the right triangle ABC wherein AB is the hypotenuse, BC is the opposite and CA is the adjacent tanA=0.45. The approximate length of AB which is the hypotenuse is 22, Opposite (BC) is 9 and Adjacent (CA) is 20. You need to use pythagorean formula in getting the length of AB.
YOUR ANSWER IS (22).
A ^ 0 = 1.
This is the final solution.