Quadrilaterals are four sided figures. The interior angles will always add up to 360 degrees. It is simply a matter of adding the lengths of the sides to get the perimeter of any shape. 

 

Parallelogram

Parallelograms have two pairs of parallel sides and opposite angles that are equal each other.

 

Rectangle

Rectangles are parallelograms where all of the angles are right angles, which makes the opposite sides of a triangle equal. 

 

Square

Squares are parallelograms where all of the angles are right angles and all of the sides are the same length. All sides of a square are equal lengths, so if a square is split on the diagonal it will form two isosceles right triangles - known as two 45-45-90 triangles. This will help make it easy to find the length of a side of the length of the diagonal depending on what the SAT question wants as an answer.