Question

How much pure antifreeze must be added to 30 L of a solution that is 40% antifreeze to make a solution that is 60% antifreeze?

Answer 1

Equate something:
A = the amount of pure antifreeze to add.

Equate Antifreeze

(30 L * 0.40) + (A * 1.00) = [(A + 30 L) * 0.60]

Equate Non-Antifreeze

(30 L * 0.60) + (A * 0.00) = [(A + 30 L) * 0.40]

Stare at both of thise until they both soak in. Which is easier to solve?