A variable is a quantity that can change; the word also refers to the letter or symbol that represents this quantity. In a proportional relationship, one variable is the independent variable, and one is the dependent variable. They are often called "x" and "y," but any letters can be used. The value of the dependent variable depends on the value of the independent variable. In the relationship between number of scoops of ice cream and total price, we can call number of scoops "x" and total price "y." Y is dependent because its value depends on x, the number of scoops you purchase. Ursula makes $5 for every 1 dog she walks. In the relationship between dollars earned and dogs walked, is the dependent variable, which is often called .