Question

How much pure acid should be mixed with 2 gallons of a 40% acid solution in order to geta 70% acid solution?

im having a hard time coming up with the equation

Answer 1

0.7(2+x) = 0.4(2) + 1.0(x), the 0.7 is the 70% you want, 0.4(2) is what you have initially, and pure acid means 1.0 or 100%.