The simplest way to write a rule for this is to write it in slope intercept form, y=mx+b. Let y represent the cost of the membership. Every month the cost is 15 dollars. If we let x represent the months we can rewrite this as 15x. The one time cost is 25 dollars so we can just add that to the end of the equation. y=15x+25. There are 12 months in a year so we just have to substitute. y=15(20)+25=205 so the answer is 205 dollars.
