A group of 30 students want to see the show at the theater. Tickets cost $7 for each student who is a member of the theater club and $12 for each student who is not a member. The total cost of the students' tickets is $300. 1. Let x represent the number of students in the group who are members of the theater club. Write an expression in terms of x for the number of students in the group who are not members.