Did you or your child/grandchild see the link I gave the other day on how to solve these, bob? I think it was BBC bitesize.
Rather than get into issues about moving sides and changing signs it's sometimes easier for these one-step problems to put your finger over the term involving the letter/algebraic symbol- in this case the 3h.
That leaves you with 8=8 minus whatever is under your finger.
So what's under your finger must be zero.
So if 3h=0 then 1h (written as h for short) must =0.
3h means 3 x h, by the way, rather than 3+h (which is what you suggested on another thread)