Jenn and David shared a candy bar. Jenn ate three tenths. David ate four tenths. How much is left?
1/10
3/10
1/2
7/10
The total amount eaten by Jenn and David is 3/10 + 4/10 = 7/10.
Therefore, the amount left is 1 - 7/10 = 3/10. Answer: \boxed{3/10}.