Question

A membership to the gym costs $23 per person in 1995. The membership cost has increased by an average of $6 per person for each year since 1995.
a. Write a linear equation for the cost of a gym membership for one person since 1995.
b. What is the cost of a gym membership in 2009?
c. What year did the gym membership cost $85?

Answer 1

Y= membership cost in year x
x=year ////
A=6(x-1995) + 23=Y
6(2009-1995)+23=Y ---> 6*14 +23=84 +23=107

Answer 2

A) The membership cost starts at $23 and it adds $6 every year. The 23 would be your b and the 6 would be your slope, m, in the form y=mx+b.
y=6x+23
This equation means that you're starting at 23 dollars and adding 6 dollars with every x you add.

B) 2009-1995=14 This means that there's 14 years that the cost increased. 14*6=$84 The membership cost increased by anther $84 over the 14 years. You have to add 84 to 23 to find your total=$107. 

C) Set $85 equal to 6x+23
85=6x+23
6x=62
x≈10
10 years later the cost will be $85. 
1995+10=2005