If the probability of a spinner landing on red in a game is 1/5, what is the probability of it not landing on red?

P (A) - probablity of a spinner landing on red

P (A') - probablity of it not landing on red.

From formula:

P (A) + P (A') = 1 Substitute P (A) = 1/5:

1/5 + P (A') = 1

P (A') = 1-1/5

P (A') = 4/5 = 4/5 * 100% = 80%

So this probablity is 4/5 (or 80%, if you want to have it on a percent)