Answer:
72
Explanation:
The LCM is when you find the lowest factor that 2 or more numbers share.
For 8 and 9,you would just need to keep multiplying each other until you find the same numbers. It would look something like this.
8,16,24,32,40,48,56,64,72..... etc.
9,18,27,36,45,54,63,72,81..... etc.
You can see how they both have the same factor (72), and since that is the lowest factor (which means I can find a lower factor then 72) then your LCM of 8 and 9 should be 72 :)