​what is the LCM of 9 and 15

The answer is 45

Prime factor both numbers

9 = 3 x 3  = 3^2

15 = 3 x 5

We pick each unique factor along with its higest power.......

This gives us 3^2 and 5

Take the product of this

3^2 x 5   =   

9 x 5  =

45       and this is the LCM