All the keys are from humble bundle January.
To redeem a game, send the answer to the equations as a comment. The first correct comment I see is the first to get a code, even though you are the first to comment, it doesn't mean you get it, sorry.
Sonic Frontiers | x+5=12
Tomb Raider IV-VI Remastered | 3x=18
Etrian Odyssey II HD | x−7=10
Nice Day for Fishing | x+2=8
Metal Slug Tactics | 2x+3=11
Settlement Survival | 4x=20
Wizard of Legend 2 | 10−x=4
Answers should be:
GAME | answer
EDIT:
All codes have now been given away, the winners have received a DM with the code