Hey!
Finding the factorial for the first few numbers, we have:
1!=1
2!=2
3!=6
4!=24
5!=120
6!=720
7!=720*7
8!=720*56
What we can see as a clear pattern from 5! and on is that our number ends with a 0, making the units digit 0. Therefore, when we add the units digit of 5! and on, we have a result of 0. So, we can simply add the units digits of 1!, 2!, 3!, and 4!, which is 1+2+6+4=13. Since the units digit is the last number, we can drop the tens place to get an answer of 3.
Feel free to ask further questions!