The formula to convert degrees Fahrenheit to degrees Celsius is:

```

°C = (°F - 32) × 5/9

```

Where:

* °C is the temperature in degrees Celsius

* °F is the temperature in degrees Fahrenheit

So, to convert 99 degrees Fahrenheit to degrees Celsius, we substitute 99 for °F in the formula:

```

°C = (99 - 32) × 5/9

°C = (67) × 5/9

°C = 37.22

```

Therefore, 99 degrees Fahrenheit is equal to 37.22 degrees Celsius.