The position of known rational numbers on the number axis is shown in the figure, which is simplified as follows: | a + B | - | A-B | - | - B |

The position of known rational numbers on the number axis is shown in the figure, which is simplified as follows: | a + B | - | A-B | - | - B |

From the number axis, we can get a + b > 0, b > 0, A-B < 0, so we can get: | a + B | - | - A-B | = a + B - (B-A) - B = a + B + a-b-b = 2a-b