This was so fucking easy. I fail to see how anyone screwed it up. Divide by 5 is good. Same concept I used. I just moved the decimal one spot over to the left, then doubled it and added it to the original number. 45 becomes 4.5 4.5*2=9 9+45=54 This is basic math. If you can't do this without fucking up, how on earth do you leave a tip in a restaurant?