Problem #11:
Twice a number (n) decreased by 5 is at least 11.
2n - 5 is = to or greater than 11.
2n - 5 is = to 11 comes out as 2n = 11 + 5, or 2n = 16, or n = 8.
If n = 8 or is greater than 8, 2n=5 will be at least 11.
Please, start work on the problems you haven't yet done. I'd be happy to comment on your own work and help you bring the solution to conclusion.