Here's how to convert 90 degrees Fahrenheit to Kelvin:

1. Convert Fahrenheit to Celsius:

* Subtract 32 from the Fahrenheit temperature: 90 °F - 32 = 58 °F

* Multiply the result by 5/9: 58 °F * (5/9) = 32.22 °C

2. Convert Celsius to Kelvin:

* Add 273.15 to the Celsius temperature: 32.22 °C + 273.15 = 305.37 K

Therefore, 90 degrees Fahrenheit is equal to 305.37 Kelvin.