A spinner has equal sections numbered 1-8. If you spin the spinner once, what is the probability that you will not get a 5?

The of the result not being 5 is just one minus the probability of getting a 5 which is ##7/8##.

Another way to look at this is that if we know the probability of the result being 5, then the probability of it not being 5 is just one minus that probability. We know that 5 is just one out of the 8 possibilities, so

##P_5=1/8##

So the probability of not 5 is

##P_("not" 5)=1-P_5 = 1-1/8 = 7/8##