A membership at a yoga studio costs $35 per month. Write an equation for the cost of the membership, c, that you pay if you keep your membership for m months.

If a membership for a yoga studio costs $35 ea. month, then here's the equation we set up.
c - Cost of membership
m - Months we want to keep it.
35 * m = c

Example:
Since the membership is $35 per month, let's say we want to keep it for 5 months. The equation will look like this:
35 * 5 = $175

No solution : there is no number of boxes that she bought