One canned juice drink is 20% orange juice; another is 10% orange juice. how many liters of each should be mixed together in order to get 10L that is 13% orange juice

Let A, B represent the amount of 20% drink and 10% drink.

A+B = 10

0.2A + 0.1B = 0.13*10

Use substitution

From 1st equation

A = 10 - B

Substituting into 2nd equation

0.2 (10-B) + 0.1B = 1.3

Distribute

2 - 0.2B + 0.1B = 1.3

Combine like terms

-0.1B = - 0.7

Divide by -.1 on both sides

B = 7

Substituting back into 1st equation

A = 10 - 7 = 3

Therefore 3L of 20% drink should be mixed with 7L of 10% drink.