Passage: . Every point of a number line is assumed to correspond to a real number, and every real number to a point.The integers are often shown as specially-marked points evenly spaced on the line.  Although this image only shows the integers from −9 to 9, the line includes all real numbers, continuing forever in each direction, and also numbers not marked that are between the integers. It is often used as an aid in teaching simple addition and subtraction, especially involving negative numbers.

Question: Which mathematical processes can an integer line can help teachers explain?
simple addition and subtraction