Try shutting of things that could distract you. (Television, phone, computer etc.)
Get away from noise; go somewhere quiet.
The answer to this question is 60 degrees.
The greatest common factor (or GCF) is, as the name says, the greatest factor a set of numbers have in common. We can find this by listing out all the possible factors (multiples) of each number:
For 28:
<u>1</u>, <u>2</u>, 4, <u>7</u>, 14, 28
For 42
<u>1</u>, <u>2</u>, 3, 6, <u>7</u>, 21, 42
<em>(note you don't need to list out all the factors, I just did it for visual purposes)</em>
As you can see, 28 and 42 have 3 factors in common, with 7 being the greatest.
Therefore, the answer would be C: the GCF is 7.
<em>Hope this helps! :)</em>