Raj bought a 20-ounce can of powdered lemonade mix. he already has used some of the mix. each quart of lemonade requires 2.5 ounces of the mix. let q represent the number of quarts of lemonade raj has made so far. which expression represents the amount of powdered lemonade mix left in the can?

For this case, the first thing we must do is define variables.
 We have then:
 q = represent the number of quarts of lemonade Raj has made so far.
 p = represents the amount of powdered lemonade mix.
 We then have the following linear equation:
 p = -2.5q + 20
 
 An expression represents the amount of powdered lemonade mix left in the can is:
 p = -2.5q + 20

Are you trying to figure out the volume?