Let: x = m+3 n

Both: x+5 = m+3 n+5.

There are (x+5)/11= x/11+5/1.

So when m+3 n is divisible by 1 1, it is 5/1,so m+3 n+5 cannot be divisible by 1 1.

Personal opinion, for the landlord's reference only ~ ~ ~