Ryan showed Brandon the following four-digit number: 2002. He then told Brandon “I am thinking of a six-digit where I have added two ones to the original number. If you can guess my six-digit number in one guess, I’ll do your chores for a week.”

What is the probability that Brandon guesses correctly with his one and only guess?

There are 5 places where he can add the 1st digit

So, there are 6 places where the 2nd can go.
So, 1 right guess out of 30 possibilities...
Almost. You have to reduce that total by the half the number of values where the two 1s are together, since they are the same