代数式是指用基本的运算符号把数或表示数的字母连接而成的式子．在学习中，我们不仅要掌握列代数式的方法，更要注意列代数式在解题中的应用．例1一家三口准备外出旅游，甲旅行社说：“着父亲买全票一张，其他人可享受七折优惠．”乙旅行社说：“家庭旅游可按团体票计价，即按 Algebraic expressions are formulas that use basic arithmetic symbols to join numbers or letters representing numbers. In learning, we must not only master the algebraic approach, but also pay attention to the application of the column algebraic approach in solving problems. Example 1 A family of three preparing to travel, A travel agency said: “With his father bought a full ticket, other people can enjoy a discount of 30%.” B travel agency said: "Family tourism can be priced according to group votes, that is, according to