Variables and expressions are essential for doing mathematics. Especially abbreviations of the multiplication sign ${ imes}$ and the division sign ${div}$ are current rules that we usually follow. In this paper, we devised a Card-Game for exercising abbreviations of the multiplication sign ${ imes}$ and the division sign ${div}$ in calculating expressions, designed a teaching unit for the calculation of expressions using the Card-Game in the variables and expressions strand, and discussed the implications of using the Card-Game for motivating students, cooperative learning, diagnosis and correction of errors, and so on.