The pool membership has an initial fee of $350, afterwards you have to pay $125 per month.
Let "x" represent the number of months of the membership and "y" represent the total cost after x months, you can express the relationship between the number of months of the membership and the total cost as:
![y=350+125x](https://img.qammunity.org/2023/formulas/mathematics/college/nxpsvjxrmtxer32gwxrc71758dxa50jg8p.png)
The family paid $1350 for the membership, to determine the number of months they paid "x", you have to replace the equation with y=1350 as follows:
![1350=350+125x](https://img.qammunity.org/2023/formulas/mathematics/college/af7b6uno3a5gkdddt19jne3298o0yo1aq8.png)
To calculate the value of x, first, pass 350 to the other side of the equation by applying the opposite operation to both sides of it:
![\begin{gathered} 1350-350=350-350+125x \\ 1000=125x \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/az71a53dp8zkabe7oj8kgegqt7dujdd4n3.png)
Next, divide both sides by 125 to reach the value of x:
![\begin{gathered} (1000)/(125)=(125x)/(125) \\ 8=x \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/cktohpxolx1yn19yh2acq2zh3rjbpyqg1j.png)
The family used the pool for 8 months.