Math question

I have a head cold so I can’t think straight but walk me through this. I was buying baby wipes and couldn’t figure out which package is cheaper. Help me out just so I don’t totally feel like I’ve forgotten everything I learned in school.

A) buy two get one free. Let’s say to make it easy, each package had 20 wipes at $3 each

B) not on sale. Let’s say it was 100 wipes for $7

Which was the better deal? Please walk me through the math/how you got there. I’m feeling a little slow today.