Sam has 4 digit bank code number that uses one button from each row. How many different possibilities for the bank no.?
1 2 3
4 5 6
7 8 9
How many possible choices does he have for the second digit?
How many possible choices does he have for the third digit?
Now use whatever method they taught you (plugging into a formula, making a "tree", etc) to find the total number of combinations.