how do I find out a slope intercept form equation with word problems?

Question

so this is the problem.." Jon purchases $15 ties and he has a $10 coupon off the total amount. Write the equation to determine what he will spend in slope intercept form".

Answer 1

The cost increases $15 every for every tie that is purchased...

So the slope is m=15

THe line equation is C(n) = 15n-10 where n is the # of ties purchased and C(n) is the cost