Which of these expressions requires a variable? A
the expression for how much money Abe earns when he makes $15 an hour and works for three hours B.
the expression for the number of pencils Cody has is if he starts with nine pencils and then gives four to Molly C.
the expression for the total number of cakes when Cindy brings one cake to class, and Bryan brings two cakes to class D.
the expression for how many birthday parties Pia has this June if she has one more birthday party than her brother