I’m a small contractor so I deal with customers on a daily basis, but not nearly the volume of a server. I was sitting at a bar drinking while waiting for a take out order. An old white dude paid with cash next to me. The server had to make change from her own wallet because they don’t have a regular register here. She had a hard time making change because she didn’t have the best bills. Old dude told her she should have paid better attention in math class. She exclaimed, I just don’t have the right bills. Gives him his change and he smugly asks for her to get him two fives for a ten. She obviously has to leave and come back with his two five. What an ass. I gave him a shitty look, but didn’t want to escalate the situation, everything I could think to say was out of anger. What’s the right thing to do here?