Christian got a haircut yesterday afternoon. If the hair stylist charged $18 and Christian gave a 20% tip, how much did he pay for the haircut?
The tip amount is 20% of $18, or (20/100)*18 = $<<20/100*18=3.6>>3.6
Including the tip, Christian paid $18 + $3.6 = $<<18+3.6=21.6>>21.6 for the haircut. Answer: \boxed{21.6}.