To join a local square dancing group Jan has to pay a $100 sing-up fee plus $25 per month . Write a equation for the cost (y) based on the number of months (x)

We know that for each month you're a part of the group, you're paying $25, so we can model that as , where is the number of months that you have been a part of the group.

We also know that you have to pay a one-time fee of $100 to join the group, so that should be added to the monthly fees you are paying, which would be .

Setting this to gives you the equation for how much money you pay for the group membership: