That would depend on the price u r originally paying because ur tip is a percentage of the original price.
Lets say u went out to eat and ur meal costs u $ 40. U plan on leaving a 20% tip. So ur tip would be 20% of 40....0.20 * 40 = 8...so a 20% tip on ur meal would be $ 8.
but if ur meal cost $ 25....and u left a 20% tip....20% of 25 = 0.20 * 25 = 5...so if ur meal was $ 25 and u left a 20% tip, u would be tipping $ 5