Chapter P, Prerequisites - Section P.2 - Real Numbers - P.2 Exercises - Page 16: 45

See below

a) $B \cup C$ means we are looking at what is included in both sets. C considers all numbers from $5 $ inclusive to $-1$ inclusive. $B$ is all numbers less than 4. When conjoining these sets, we get (-∞, 5]. b) $B \cap C$ means the intersection and the intersection is between $-1$ and $4$ BUT, the set is noninclusive. $(-1,4)$