A question about the third lesson "subtraction of rational numbers" in the first volume of junior one mathematics. (Compulsory Education Curriculum Standard Experimental Textbook)
In other words, the formula should be written without brackets, and a negative number is a positive number. For example, what you see is -(-6), which means there are two minus signs in front of the brackets. At this time, two negative signs become a positive sign, which is +6. Of course, it is the same as +(+6). If a number is preceded by a negative sign and a positive sign, such as +(-7), then the positive sign is not written directly.