Answer:
you can go to the gym for 21 months.
Explanation:
1.) Organize: membership per month= $20, down payment= $80, to spend= $500.
2.) Make an equation: 20m+80<500.
3.) Solve: (subtract the down payment first) 500-80= 420 (divide 420 ($ left after the downpayment) by the monthly fee) 420/20= 21.
4.) Convert: (make sure not to mix up with numbers and subtract and or divide by the wrong numbers!) 21m.
5.) Finalize: you can go to the gym for 21 months.
Hope this helps! Comment below this if you have any questions :)