"<span>Start by setting up the standard equation for perimeter of a parallelogram, P=2w+2h (these variables of course being width and height). </span> Now, substitute in what you know...
<span>The problem tells us that width is equal to height minus four. This means that, in order to keep only one variable in this problem, we will write width as h-4. </span> <span>The problem also tells us that 72 is the perimeter, so we substitute that for P. </span>
72=2(h-4)+2h <span>Now solve from here. </span> <span>(Distribute first) </span> 72=2h-8+2h (Combine like terms) 72=4h-8 80=4h (Isolate h) 80/4=h <span>20=h"</span>