Answer:
2a
Step-by-step explanation:
Look at the numbers first: 12, 28, 42
12 = 2 * 2 * 3
28 = 2 * 2 * 7
42 = 2 * 3 * 7
The only factor all numbers have in common is 2.
GCF of numbers = 2
Now look at the variables: a^2b^6, a^4, ab^3
a^2b^6 = aabbbbbb
a^4 = aaaa
ab^3 = abbb
The only variable all expressions have in common is a.
GCF of variables = a
GCF of the three monomials is: 2a
