1/12
Convert them both to have the same denominator.
1/3 ÷ 4
1/3 ÷ 12/3
When dividing fractions, you flip the second fraction and multiply instead.
1/3 ÷ 12/3 = 1/3 × 3/12
1 × 3 = 3
3 × 12 = 36
3/36
This can be simplified by dividing by 3.
3/36 = 1/12