Substitution method, mixture problem

Question

A chemist needs 15 liters of a 60% alcoholic mixture. The chemist has a mixture that is 50% alcohol. How many liters of the 50% alcohol solution and pure alcohol should the chemist mix together to make 15 liters of a 60% alcohol solution?

Answer 1

x = liters of 50% alcohol

15 - x = liters of 100% alcohol

 

(50%)x + (100%)(15 - x) = (60%)(15)

 

Solve for x.

 

-50x = -600

 

x = -600/-50 = 12

15 - x = 3

 

You need 12 liters of 50% alcohol, and 3 liters of 100% alcohol.

 

Answer 2

0.50x + (15 - x) = 0.60(15)

 

Can you solve for x and answer?