Answer:
You will need 10 gallons of pure acid to mix with 5 gallons of a 70% acid solution to get a 90% solution.
Step-by-step explanation:
.70(5) + x = .90(x + 5) I want to multiply both sides by 100 to clear the decimal
70(5) + 100x = 90(x + 5) Distribute the 70 and the 90
350 + 100x = 90x + 450 Subtract 90x from both sides
350 + 10x = 450 Subtract 350 from both sides
10x = 100 Divide both sides by 10
x = 10
