Jonathan S. answered • 05/22/20

R expert. Patient, knowledgable, and experienced statistics tutor.

Imagine 6 blank slots we must fill

_ _ _ _ _ _

The first slot must have a letter, there are 3 options for which letter to choose.

The last slot must be a number, there are 3 options for which number to choose.

After we choose a starting letter and an ending number, there are 4 characters left (2 letters and 2 numbers), which can be arranged in 4! ways.

3*3*4! = 216.