I need to find the percent of pure juice in the can of concentrate by creating a system of linear equations with two variables

Question

I need help solving it but I want a detailed explanation.

The label on a 12-ounce can of frozen concentrate Hawaiian Punch indicates that when the can of concentrate is mixed with 3 cans(36-ounces) of cold water the resulting mixture is 10% fruit juice. Find the percent of pure juice in the can of concentrate.

Answer 1

10% of the 36 ounces is juice. Therefore 3.6 ounces are juice

3.6 / 12 = 0.30

 

The 12 ounce can is 30% juice.

 

(Credit to Arthur D.)