Chapter 13 - Counting and Probability - 13.2 Permutations and Combinations - 13.2 Asses Your Understanding - Page 855: 37

$60$

The order of the letters matters here, so the situation involves permutation. We know that $P(n,r)=\frac{n!}{(n-r)!}.$ Hence with $n=5$, $r=3$, then: $P(5,3)=\frac{5!}{(5-3)!}=\frac{5\cdot4\cdot3\cdot2!}{2!}=5\cdot4\cdot3=60.$