Add the chicken and mackerel fractions, then subtract from 1 whole.<br><br>
&bull; Chicken + mackerel: \( \frac{5}{12} + \frac{1}{3} = \frac{5}{12} + \frac{4}{12} = \frac{9}{12} = \frac{3}{4} \)<br>
&bull; Vegetable = \( 1 - \frac{3}{4} = \frac{1}{4} \)<br><br>
Check: \( \frac{5}{12} + \frac{4}{12} + \frac{3}{12} = \frac{12}{12} = 1 \). ✓<br><br>
Final Answer: \( \frac{1}{4} \)