Not quite. Can you show your work so that we can pinpoint any errors you have made? To start, you know the average is 4. So, the sum of all the numbers divided by the number of numbers is equal to 4:
You want to find the average of x, 1, and 2 (the sum of these numbers divided by 3 since there are 3 numbers now):
Can you think of a way to use the first equation to get the average in the second equation?