Question 362372
How many litres of a 12% alcohol solution must be mixed with 8 litres of a 3% alcohol solution to make a 9% solution

12x/100    +   8 . 3 / 100 =  (x + 8 ). 9 / 100

12x  + 24  = 9(x+8)

3x         = 48 

 x         = 16