You want to paint a room in your house. A technician of Home Depot uses the computer to analyze your current paint and tells you that it is a 22% blue paint. However, Home Depot only sells 20% blue and 30% blue paints. How many gallons of 20% and 30% paints you need to mix to make 10 gallons of 22% paint??

(.8 gallons) x (20% paint) + (.2 gallons) x (30% paint) = (1 gallons) x (22% paint).

Multiply the gallons by 10:

(8 gallons) x (20% paint) + (2 gallons) x (30% paint) = (10 gallons) x (22% paint).