Given the position of numbers a, B, C on the number axis as shown in the figure, try to simplify | a + C | - | a + B + C | - | B-A | + | B + C | ---------c----b--------0----a--------

Given the position of numbers a, B, C on the number axis as shown in the figure, try to simplify | a + C | - | a + B + C | - | B-A | + | B + C | ---------c----b--------0----a--------

|a+c|=-(a+c)
|a+b+c|=-(a+b+c)
|b-a|=-(b-a)
|b+c|==-(b+c)
So | a + C | - | a + B + C | - | B-A | + | B + C | = - [(a + C) - (a + B + C) - (B-A) + (B + C)] = b-a-c