Abig department store employs a total of 180 people. of these 180 people, 27 are managers, 100 are floor assistants, and the rest are . if we choose an employee at random, find the probability that the employee is not a floor assistant.

Among 180 people 27 are managers, 100 are floor assistants and the rest are helpers. Under the rest we mean 180-27-100=53 people.

The event "randomly selected employee is not a floor assistant" is the same as "randomly selected employee is manager or helper". You can count that in total 27+53=80 people form the set of managers and helpers.

Then the probability that randomly selected employee is not a floor assistant is

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.