In Closing The rules for adding and subtracting integers apply to all rational numbers. The sum of two rational numbers (e. g., −1 + 4.3) can be found on the number line by placing the tail of an arrow at −1 and locating the head of the arrow 4.3 units to the right to arrive at the sum, which is 3.3. To model the difference of two rational numbers on a number line (e. g., −5.7 − 3), first rewrite the difference as a sum, −5.7 +(−3), and then follow the steps for locating a sum. Place a single arrow with its tail at −5.7 and the head of the arrow 3 units to the left to arrive at −8.7.