To answer this question, we have that:
1. Jenn ate 3/10 of a candy bar.
2. David ate 4/10.
The amount of candy that is left is:
We have that the total is 10/10 = 1. We used fractions with the same denominator so we can only need to subtract the numerators. We need to subtract the total amount eaten by Jenn and David (3/10 + 4/10 = 7/10).
Therefore, the left candy is equal to 3/10 (option B).