A gym offers two different membership options. In the first option, new members pay a one-time fee of $50 and a monthly fee of $30. In the second option, members pay a one-time fee of $100 and a monthly fee of $20. To find out when the cost will be equal, you will need to solve for m using substitution. Substitute the expression for the cost from the first equation into the cost, c, in the second equation.