the distance formula to find the length of the sides... opposite sides equal it could be a rectangle or parallelogram all sides equal, square or rhombus adjacent equal, kite and then the slope is used to check angles if the product of the 2 lines in -1 the lines are perpendicular (right angle) the the slopes of 2 lines are the same the sides are parallel.
If all the angles add up to 90 degrees then you can set the equation 7x-9*2x=90 Simplify 9x-9=90 Plus 9 both sides 9x=99 Divide by 9 on both sides X=11
