Chapter 2 - Real Numbers - Chapters 1-2 Cumulative Review Problem Set - Page 91: 27

4

First, we express each number as a product of its prime factors: $28=2\times2\times7$ $36=2\times2\times3\times3$ $52=2\times2\times13$ Since two 2s are common to both of the numbers, we obtain: Greatest Common Factor$=2\times2=4$