What is the mechanism for awarding extra reputation to an answer?
The system is network wide so can't be changed just for tex.sx, so you'd need to raise a change request on the main meta. Note that one user known for offering "2000 point" bounties does that by awarding bounties of 500 points on different questions.....
So if you want to bump someone by 75 points, choose any good answer of theirs and give them 75. You can give a bounty giving the standard reason Reward existing answer. See http://blog.stackoverflow.com/2011/09/bounty-reasons-and-post-notices
If you are willing to offer some of your own reputation for a correct answer, set a bounty.
According to the help center reputation are gain in particular for:
- answer is voted up: +10
- answer is marked “accepted”: +15 (+2 to acceptor)
- bounty awarded to your answer: + full bounty amount
- one of your answers is awarded a bounty automatically: + half of the bounty amount (see more details about how bounties work)
So you can add a bounty as @smpl suggests in his answer.
But you may also want to accept answer which gave 15 rep points to the answer's OP. This enables one to track easily the answer that the OP judges the more useful.