Answer:
15 sour candies.
Step-by-step explanation:
since David already is buying a peppermint for $.10 the first thing you would do is subtract $.10 from $4.
$4.00-$0.10=$3.90
Since we already know that 4x.25=1 we would get 4 for each 1 whole dollar so since we have 3 whole dollars you would multiply 3x4 to get 12, then you since .10 isn't more than .25 we would only be able to get 3 sour candies from .90 which would add to our 12 to get 15