How many vehicles can a state license if it uses 3 letters and 3 digits on each tag, and both digits and letters may repeat?

Since there are 10 options for a digit (I think) and 26 letters, we can do

26*26*26*10*10*10 = 4096 * 10^3 = 4096000 if the letters and digits have to be in the same place.

If you can rearrange them, it's 36^6 (36=26+10) = 2176782336