if you add one number divisible by n and one number not divisble by n will the result be divisible by n?

and..

if you add two numbers not divisible by n will the reult be dvisible by n? explain.

(a) No, it won't. The remainder will be the same as that for the number that isn't divisible by n.

(b) It might be, and it might not. Consider whether (8+4) is divisible by 3, given that neither 8 nor 4 is divisible by 3; then consider whether (8+5) is divisible by 3, given that neither 8 nor 5 is divisible by 3.