Bob has 7 pairs of slacks and 33 shirts.
How many different ways could he select a slack and shirt combination?
For the 1st pair of slack Bob has 33 different choices of shirts.
For the 2nd pair of slack Bob has 33 different choices of shirts.
For the 3rd pair of slack Bob has 33 different choices of shirts.
Do you see the pattern?
This simply means that we have to multiply the total pairs of slacks and the total number of shirts to get all the possible combinations.
Therefore, Bob can select a slack and shirt in 231 different ways.