For this case we have that by definition, the Greatest Common Factor (GCF) is the largest factor that 2 numbers have in common.
So, we have the following expressions:

We look for the positive integers that divide to 35 and 42 without leaving residue:
42: 1,2,3,6,7,14,21
35: 1,5,7
Thus, the GCF of 42 and 35 is 7
Then, the GCF of the three expressions is:

Answer:

1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, he ran 4.5 miles 5 weeks ago
Answer:
Add a radical term to both sides and square both sides only once.
Step-by-step explanation:
I believe this is the answer but someone may provide a better answer.