Know how and how much to tip people who expect gratuities, even in the case of poor service.
Success may be the ability to be happy with whatever we're stuck with.
Know which officials are voted into office and which are appointed, and by whom.
Profit is what we have left after we make a donation to a worthwhile cause.
I suspect that some apparently homosexual people are really heterosexuals who deeply phobic about the opposite sex or have other emotional problems.
Geometry is beautifully logical, and it teaches you how to think and prove that things are so, step by step by step. Proofs are excellent lessons in reasoning. Without logic and reasoning, you are dependent on jumping to conclusions or - worse - having empty opinions.