Years ago there was a trend on credit card tabs at restaurants to list a handy guide to tipping. This saved customers the trouble of having to do math, which I have to guess had a positive effect on how much of a tip people left.
That trend never caught on, but recently at a restaurant here in Seattle (Agave) I saw it again.
The one thing that is missing here is offering the total. Why only do half the math?
Instead of saying “15% = $14.55”, it should say “15% = $14.55 = 120.77”.