Describe and correct the error : |-13| - |13| = - 13 - 13 = 26

First,

|-13| represents the absolute value of the number 13. Absolute values cannot be negative. So |-13| cannot become - 13, it would become 13.

So,

|-13| - |13| = - 13 - 13 = 26 would become

|-13| - |13| = 13 - 13 = 0