(Pressure) * (volume) = (# moles) * (gas constant) * (temperature)

The ideal gas law.

In another thread I admit I didn't explain my position here well enough. I would only not explain this equation given sufficient context (e.g. I've shown all those variables in a table, and my intended audience is people familiar with basic chemistry, which I'd expect would be everyone reading the report for this particular example, since this is high school chemistry, and the topic of all reports I work on is chemical engineering.)

People can read the conclusions if they're not familiar with chemistry, and for the detail, they're not my intended audience anyway.

Generally I still hold the position that you should define variables as much as possible, unless it's overly cumbersome, given your intended audience would clearly understand anyway.

In context this simple equation is obvious even if you change the symbols, as long as there is sufficient context to draw from.