Answer:
The situation can be modelled by the function f(x)=210-15x. Where f(x) represents the amount of money on her account in $ and x the number of times she uses.
Explanation:
As we know each linear function can be expressed as:
f(x) = mx + b
Where m is the rate of change, b the initial value and x the independent variable.
In this particular example, Gisselle provides on $210 in her account at the beginning, that is the initial value m. As $15 is discounted for each time she uses the club, then 15$/times, represents the rate of the linear function.