solving a percent mixture

Question

Problem Page

The Royal Fruit Company produces two types of fruit drinks. The first type is 40%

 pure fruit juice, and the second type is 100%

 pure fruit juice. The company is attempting to produce a fruit drink that contains 55%

 pure fruit juice. How many pints of each of the two existing types of drink must be used to make 180

 pints of a mixture that is 55%

 pure fruit juice?

Answer 1

a + b = 180

0.4a + b = 180(0.55)

Here's how I'm gonna solve this one.

b = 180 - a

b = 99 - 0.4a

180 - a = 99 - 0.4a

0.6a = 81

a = 135 pints

b = 180 - 135

b = 45 pints