A gym membership costs $20 per month plus a one-time fee of $30. If Josh paid $90, write an equation to determine how many months he paid for.

To determine how many months Josh paid for, we can set up the following equation based on the information provided.

Let \( x \) be the number of months Josh paid for. The total cost can be calculated as follows:

1. There is a one-time fee of $30.
2. The cost for the gym membership for \( x \) months is \( 20x \).

The total cost equation will be:

\[ 30 + 20x = 90 \]

Now, we can solve for \( x \):

1. Subtract the one-time fee from both sides:

\[ 20x = 90 - 30 \] \[ 20x = 60 \]

2. Now divide both sides by 20:

\[ x = \frac{60}{20} \] \[ x = 3 \]

So, Josh paid for 3 months. The equation we used to determine the number of months is:

\[ 30 + 20x = 90 \]