When doing the laundry, you use 6 cups of detergent for every 7 gallons of water. Which of the following equations can be used to calculate c, the number of cups of detergent needed when using 21 gallons of water?

When doing the laundry you use 6 cups of detergent for every 7 gallons of water Which of the following equations can be used to calculate c the number of cups o class=