Can someone help me with this? Thanks!

b=4

Step-by-step explanation:

4b+5=1+5b (subtract 4b on both sides to get the b's together)

-4b         -4b

5=1+5b-4b (subtract 1 from both sides)

-1  -1

4=1b (divide by 1)

b=4

(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