Add the fractions that chose fish fingers and burgers, then subtract that sum from 1.
Fish fingers: 2/5
Burgers: 1/3
Sum of fish fingers and burgers fractions:
2/5 + 1/3
Common denominator = 15
2/5 * 3/3 + 1/3 * 5/5 = 6/15 + 5/15 = 11/15
Now we subtract 11/15 from 1.
1 - 11/15 = 1/1 * 15/15 - 11/15 = 4/15
The fraction that chose chicken nuggets is 4/15.