Explain my mistake and help me answer it

its not 9xb its 9b

Step-by-step explanation:

yes its multiplying but you are not directly putting that  

Write it as 9b = 36

Step-by-step explanation:

As you move into more complex math, the symbol for multiplacation will be an * or a dot. the "x" is used as a variable, so that is why the computer said it was wrong

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18