What is the greatest common factor of these? 27y^7x^8w^4 and 18y^3w^6

First, look at the coefficients. They are 18 and 27, which means the final answer will have the coefficient of 9, since its the GCF in between them.

Look at the xs. Since there aren't any in the second expression, it's not part of the answer.

Now, look at the ys.
The GCF in between y^7 and y^3 is y^3.

Finally, look at the ws.
The GCF in between w^4 and w^6 is w^4.

Put them all together, and the answer is 9y^3w^4

Hope this helps!