8: To find the probability of two events both happening, multiply the probabilities together.

10: To find the probability of any one of several events happening, add the probabilities together (and donâ€™t double-count anything).

11: The probability of an event can be expressed as a fraction in which the denominator is the number of equally likely possible outcomes and the numerator is how many of those equally likely outcomes are what you are looking for.

16: 0 is equal to 0%, and 1 is equal to 100%.

18: Consider each person in the survey to be one possible outcome.

31: What fraction of the 15,000 computers are expected to be defective?

33: Start by factoring the common monomial 3 from each term.

34: -11 needs to be split into two negative numbers so that their product will be positive.

39: The square root of 9 over 25 is the same as the square root of 9 over the square root of 25.