For the perimeter calculation you were doing great for both of these right up til the last statement. You have:

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.