Question

que. no 7 pls send me the solution

Answer 1

let a be any positive integer which on dividing by b gives q and r as quotient and remainder respectively
b=3
r=0,1,2
a=bq+r

Ifr=0
n=3q
n+2=3q+2
n+4=3q+4
hence only n is divisible by 3

If r=1
n=3q+1
n+2=3q+1+2=3a+3
n+4=3q+1+4=3q+5
hence only n+2 is divisible by 3

If r=2
n=3q+2
n+2=3q+2+2=3q+4
n+4=3q+4+2=3q+6
hence only n+4 is divisible by 3

hence only one out of n,n+2,n+4 is divisible by 3