Solution:
To find out what percentage of the sodas served were regular, you need to do the following steps:1. Calculate the total number of sodas served: regular sodas + diet sodas.2. Calculate the percentage of regular sodas out of the total number of sodas.David's Diner served 12 regular sodas and 3 diet sodas.Total sodas served = 12 regular + 3 diet = 15 sodas.Now to get the percentage of regular sodas, you divide the number of regular sodas by the total number of sodas and multiply by 100%.Percentage of regular sodas = (12 / 15) × 100%Percentage of regular sodas = 0.8 × 100%Percentage of regular sodas = 80%So, 80% of the sodas served were regular.