Perimeter = 6x + 12.
That's the answer right there, as it defines the perimter in terms of x, so no need to go on! Your next move was to say that x = 12/6, but that's wrong. Applying basic algebra you might have said this:
Perimter = 6x+12
6x = Perimeter - 12
x = Perimter/6 - 2
But that simply gives x in terms of the perimter, but that's not what they're asking.
As for the area calculation you didn't multiply the two terms correctly. Area = (2x+1)(x+5) = 2x(x+5) + 1(x+5) = 2x^2 +10x + x + 5 = 2x^2 +11x + 5.