Draw a horizontal line across the graph paper with a pencil, then make vertical marks intersecting the horizontal line, making each vertical mark approximately 1/2 inch long, and spaced equally across the width of the paper.
Label the vertical mark closest to the center of the paper with the number "0." Add numbers to each vertical mark going to the right, starting just to the right of "0" with the number "1," then make the next one to the right "2," and so on until you reach the end of the paper. Repeat for the left side of the number "0," starting with "-1," then "-2," and so on.
Locate the number on the number line that correlates to the first number in your equation. For example, if the equation is 7 - 2, circle positive 7 on the number line.
Locate the second number in the subtraction problem, and determine if it is a positive number or a negative number by looking for a "+" or "-" symbol in front of the number. Count to the left on the number line until you reach the second number if the second number on the line is a (+) positive number. For example, if the equation is 7 - 2, start at positive 7 on the number line, then count two spaces to the left to find the answer, which is 5.
Count to the right on the number line until you reach the second number if the second number is a negative number. For example, if the equation is 7 - (-2), start at positive 7 on the number line, then count two spaces to the right, to get the answer, which is 9.