Question 345078
Usually we talk about rectangles having length (shown as 'l') and width (shown as 'w'), so the P = 2l + 2w.

You have the values to substitute for 'l' and 'w' 
{{{l = z+2}}}
{{{w = z}}}

{{{P = 2l + 2w = 2*(z+2) + 2*z  = 2z + 4 + 2z}}}

Collecting terms, we have 

{{{P = 4z + 4}}}

The area is found much the same way.

We know the area (A) of a rectangle = length times width = l * w.

Substituting what we know about l and w, we have:

{{{A = (z+2) * z = z^2 + 2z}}}

Done.