Question

13. Show that exactly one of the numbers n, n + 2 or n + 4 is divisible by 3.

Answer 1

Let n be 1

n = 1
1 ÷ 3 is not exactly divisble
n + 2 = 3
3 ÷ 3 is divisble
n + 4 = 5
Not exactly divisble

So, n + 2 is divisible!