Question

HELP! what is the gcf of these monomials?

Answer 1

There's a 30 coefficient on the first and no coefficient (i.e. a 1) on the second.  So the GCF of the constant part is GCF(30,1)=1.

Similarly, $GCF(x^3, x^5)=x^3$ because both have $x^3$ as a factor.

$GCF(y^4,y^3)=y^3$ because both have $y^3$ as a factor.

Now that we see how the bits work it's not too hard to read these off:

$GCF(30x^3y^4, x^5y^3)=x^3y^3$