Simplify the expression \( \frac{3}{8}k + \frac{4}{9}k - \frac{5}{12}k \).

First, find the least common multiple (LCM) of the denominators: 8, 9, and 12. The LCM is 72. Rewrite each fraction with 72 as the denominator: \( \frac{3}{8} = \frac{27}{72} \), \( \frac{4}{9} = \frac{32}{72} \), \( \frac{5}{12} = \frac{30}{72} \). The expression becomes \( \frac{27}{72}k + \frac{32}{72}k - \frac{30}{72}k = \frac{29}{72}k \). Therefore, the simplified expression is \( \frac{29}{72}k \).