Question

Let the price of a meal at a restaurant be 'p'. The tax and tip on the meal are generally a percentage of the meal's price. The total cost of the meal is its price plus tax plus tip.

David calculates a 15% tip by dividing the meal price by 10, dividing that number by 2, and then adding the two numbers, i.e. tip=
p/10 + (p/10)/2.
Explain whether or not this method is correct.