The probability of selecting a pencil of a certain color is given by the amount of pencils of that color over the total number of pencils.
Knowing that, let's first calculate the total number of pencils:

Then, the probability of selecting a blue pencil is:

And the probability of selecting a yellow pencil is:

Now, to calculate the probability of both events happening, we just need to multiply the probabilities of each event:

So the probability is 0.09 or 9%.