Advanced math word problem

Question

How many liters of a 74% glycol solution must be added to 67 L of a 31% glycol solution to get a 59% glycol solution

Answer 1

.74x + .31(67) = .59(x+67)

.74x + 20.77 = .59x + 39.53

(.74-.59)x = 39.53 - 20;77

.15x = 18.76

x = 18.76/.15 = 125.0666... Liters of 74%

31 is within 28 of 59

74 is within 15 of 59

you need 28/15 times as much 74% as 31%

28/15 = x/67

x = 67(28)/15 = 125.0666...