I got a little but of idea for the second one...

if a = b(mod n) and c = d(mod n), then ac = bd(mod n).

So, by using the definition of the modulus:

a = b + nk and c = d + nl for some integers we'll call k and l.

So by multiplying both of these conditions we then get:-

ac = (b + nk)(d + nl)

= bd + nkd + nlb + n^2kl

= bd + n(kd + lb + nkl)

which means that ac = bd(mod n) since (kd + lb + nkl) is just some

integer.

I hope this is right!

I did the similar operation for 1st but I am still not sure on how to resolve it?

coz I keep getting the some random terms in there...

Thanks for the any help!