四则运算是数学的基础。

The four operations are the basis of math.

一个男孩儿教一个女孩儿四则运算，他说那是他的任务。

A boy was teaching a girl arithmetic, he said it was his mission.

本文的工作对进一步完善布尔代数的四则运算理论具有一定的意义。

The paper is of certain significance to improve the four fundamental operations theory of Boolean algebra.