Question

how much water should be added to 1 gallon of pure antifreeze to obtain a solution that is 60% antifreeze?

Answer 1

1 gallon of antifreeze = 60% of mixture. Total mixture:
Vm = 1/0.6
= 1.67 gallons

Volume of water = total vol - antifreeze vol
= 1.67 - 1
= 0.67 gallon of water