Manhattan 700 + Mixing Problem

Gasohol is a mixture consisting of 5% Ethanol and 95% Gasoline.
5% 0f 20 gallon = 20*5/100 = 1 gallon

Therefore, 20 gallons of Gasohol contains 1 gallon of Ethanol and 19 gallons of Gasoline.

Say, x gallons of Ethanol is mixed to achieve a mixture consisting of 10% of Ethanol and 90% Gasoline.
After mixing x gallons of Ethanol, the mixture will contain (x + 1) gallons of ethanol and 19 gallons of Gasoline.

Now, percentage of Ethanol in the mixture = [(New amount of Ethanol)/(New amount of mixture)]*100 = [(x + 1)/(x + 20)]*100

So, [(x + 1)/(x + 20)]*100 = 10
=> (x + 1) = 0.1*(x + 20) = 0.1x + 2
=> (x - 0.1x) = 2 - 1 = 1
=> 0.9x = 1
=> x = 1/0.9 = 10/9

The correct answer is C.