Question 699487
If I have 9 floors of a building, and I assume each floor is 10 feet tall, then I have a 90 ft tall building({{{9*10 = 90 feet}}}). I know that I have to pay 100 dollars no matter what for the first floor/ first 10 feet. That leaves me to pay $25 for any remaining floors. In this case, there are 8 floors remaining.

My payment is {{{100+ (25*8)}}}. However, I want an equation for every case.

Assume the number of floors = N, then for any given number of floors, I will pay $100 for the first floor/the first ten feet. I will then pay for $25 for the remaining floors which is equal to the total number of floors minus the first floor. 

Your equation to find the total cost is:
{{{100 + (25*(N-1))}}} dollars.