Explanation:
come on ! for sure you have worked with a thermometer before in your life ?
please don't switch off the brain just because it is math. keep it and your common sense active also for math problems.
you would be surprised how many you can solve just by logical thinking and applying your own life experiences. math is actually everywhere.
how many degrees from 3 to 0 ? 3
how many degrees from 0 to -5 ? 5 !
so, in total 3 + 5 = 8 degrees.
formally it is
|-5 - 3| = |-8| = 8 degrees difference.
you know the "absolute value" function that returns always the positive value of the argument, no matter if it is negative or already positive ?