How do I divide 324 by 9 in a easier way

You can think of the largest multiple of 9 that is less than 324. For example, $9 \times 30 = 270$.
So, we can write 324 as $270 + 54$.

$$\frac{324}{9} = \frac{270 + 54}{9}$$

$$\frac{270}{9} = 30$$ $$\frac{54}{9} = 6$$

$$30 + 6 = 36$$ $$36$$