It costs $100 to join a fitness center plus a monthly fee. you spent $700 last year at the fitness center. how much was the monthly fee? write and solve an equation to determine the monthly fee

100+12X=700, one time $100 plus monthly amount (X) equals $700. Subtract 100 from both sides to get the X variable alone: 12X=600. Divide by 12 to get the unknown by itself: X=50. The monthly cost is $50 :)