Chapter R - Review of Basic Concepts - R.1 Sets - R.1 Exercises - Page 8: 93

$\emptyset \cap R = \emptyset$

RECALL: (1) $\emptyset$ is the empty set (2) The symbol $\cap$ represents intersection of sets which lists down in a set the elements that are common to the given sets. Since the empty set has no elements., then its intersection with any other set will also be empty. Thus, $\emptyset \cap R = \emptyset$