Calculus
There must be a reason why they put this sign in Texas of all places, but it does prove that Texans take their math seriously, as serious as they do drinking and driving. Texans know how to have fun, but they can also be very strict when necessary, for example, when it comes to drinking and doing math problems.
But the more pressing question is – who are they hiring in all these signs? People to write new signs? It seems like Ek Arroyo is constantly hiring, judging by these signs, and it sounds like a nice place to work.