For any set of outcomes the total probability but be equal to 1, by definition:
[tex]P(total)=1[/tex]
We also know that any event and its compliment, for example [tex]A[/tex] and [tex]not A[/tex], partition the probability space, i.e.:
[tex]P(A)+P(not A)=1[/tex]
Therefore:
[tex]P(not A)=1-P(A)[/tex]
[tex]P(not A)=1-\frac{3}{8}[/tex]
[tex]P(not A)=\frac{5}{8}[/tex]
