DON'T TAKE MY FULL WORD FOR IT THOUGH I'M NOT THAT GOOD AT MATH
5. No solution
6. x = -3
8. 3 1/2x = 0 so I think it's x = 0
9. No solution
11. No solution
12. Infinitely many solutions
14. I also think no solution
15. Infinitely many solutions
I'm pretty sure like half of these are wrong.