Question 593062
    A chemist has 300mL of a solution that is 2/3 acid, She wants to make a solution that is 3/4 acid. How much acid should she add to the original solution. .
Let x = amount (mL) acid added 
then
x + (2/3)(300) = (3/4)(300 + x)
multiplying both sides by 12:
12x + (8)(300) = (9)(300 + x)
12x + 2400 = 2700 + 9x
3x + 2400 = 2700
3x = 300
x = 300 mL