Chapter 1 - Some Basic Concepts of Arithmetic and Algebra - 1.2 - Prime and Composite Numbers - Problem Set 1.2 - Page 13: 73

$12$

Factor each number completely to have: $48 = 2 \cdot 2 \cdot 2 \cdot 2 \cdot 3 \\60 = 2 \cdot 2 \cdot 3 \cdot 5 \\84= 2 \cdot 2 \cdot 3 \cdot 7$ Since two 2s and one 3 are common to both, the greatest common factor of the given numbers is: $2 \cdot 2 \cdot 3 = 12$