4. (6 points) Using the numbers $2$, $4$, $12$, and $40$ once each, you can get 24 through $\qquad$ such operations.
【Solution】Solution: $40 \div 4+12+2$,
$$
\begin{array}{l}
=10+12+2, \\
=24 ;
\end{array}
$$

Therefore, the answer is: $40 \div 4+12+2$.