Jon P. answered 02/17/15
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I can't draw it here, but let's suppose we had a parallelogram with sides 6 and 5. The perimeter would be 22, as required.
Draw the parallelogram so that the horizontal sides are 6 and the slanting vertical sides are 5, and have it slant to the left.
From the upper right corner, drop a line that is perpendicular to the horizontal sides. Now you have a right triangle on the right. The hypotenuse of the right triangle is the diagonal side of the parallelogram, which has a length of 5.
Now, suppose that the perpendicular line dropped from the upper right corner intersects the bottom at the midpoint of the bottom. So now the base of the right triangle I just described above would be 3.
By the Pythagorean theorem, the height of the right triangle would be 4.
But the height of the right triangle is the same as the height of the parallelogram. So now we know that the base of the parallelogram is 6 and the height is 4. So the area is 24, which is what you wanted.