When we change the numbers to negative what happens is the -b is farther than -a to zero. Now, -b is less than -a. Whether, a number is smaller or larger is determined by the number's distance to zero. If the number is negative the farther the number the smaller it is. If the number is positive the farther the number the larger the number is.
Let us take an example
3<4
Now their opposites are
-4 and -3.
4 3 2 1 0 -1 -2 -3 -4
Now, it can be seen that -4 is farther hence -4 is smaller than -3.
you have to take the amount of money given and subtract the total of the purchase , with the total including tax that makes it easier because you dont have to calculate it . so payment - total = change
