This is an example of a problem involving mutually exclusive events, which are events that cannot occur at the same time.
See a more detailed explanation about mutually exclusive events at this link: https://brainly.ph/question/279424
Hence, we use the formula P(A or B) = P(A) + P(B).
a. The probability of wearing a blue shirt is [tex] \frac{5}{15}= \frac{1}{3} [/tex]
b. The probability of wearing a red shirt is [tex] \frac{4}{15} [/tex]
Therefore, the probability that Rhian will wear a blue or a red shirt is [tex] \frac{5}{15}+ \frac{4}{15}= \frac{9}{15}= \frac{3}{5}[/tex] or 0.6.
