Jourdan...I'm limited by the functions of this e-mail...so I'm going to describe it to you, so that you and put a visual picture and it will help answer your own question. I'm going to describe it to you, step by step, and if you will draw it. Jourdan...I'm assuming you know the definitiond of some of the words I use. Step 1 On your sheet of paper, draw to parallel lines...(remember the definition of two parallel lines)...now that you have drawn the lines...draw a third line which intersects with the two lines...its gonna look like a railroad track with a telephone pole that fell across it at an angle and touching both lines at some point. Not at a right angle, or straight across. Step 2 This configuration creates 8 angles, 4 on one line and 4 on the other line, correct? Can you see that? this is where the rules and axioms come into play which defines 2 parallel lines. Step 3 Pick one of the lines that intersect, with 4 angles. If the lines are not right angles, you will have one group of angles, one larger than the other... that's if the lines do not create right angles. Look under the parallel line, you will see similar lines, that are upside down and reversed. Step 4 The point where the two lines intersect, the vertex, one of the angles is larger than the other. BUT...But...together, they create a straight line. Let's say one angle is Angle A, the larger angle, and the other angle, which is smaller, Angle B.(notice I have not used any measurement, like degrees!!!) SO...now we have the equation below. Angle A + Angle B = a straight line RIGHT!!!! Step 5 Look at where the lines intersect. There are 4 angles, RIGHT! We said Angle A was the larger angle. NOTICE...right across Angle A is another angle with is very similar. The angle is right across and under Angle B. Let's label that Angle D. Step 6 Since Angle D is under Angle B notice that being next to one another they create a straight line...created by the intersection of one line to another. Since Angle B and Angle C create a straight line. So we can say: Angle B + Angle D = a straight line RIGHT!! See that !!! Step 7 But remember: Angle A + Angle B = a straight line right!! But we also saide Angle B + Angle D = a straight line RIGHT!!!! Do you see what happened here.... we can say Angle B = Angle B Right!!! If this is true Angle A = Angle A and Angle D = Angle D RIGHT!! But we also said Angle A + Angle B = a straight line a nd Angle B + Angle D = a straight line And since a straight line is going to equal a straight line....we can say Angle A + Angle B = Angle B + Angle D And since Angle B = Angle B....we can then say: Angle A + Angle B = Angle B + Angle D so Angle A = Angle D With all of this said...now but in the degrees of the angles created by intersecting two parallel lines. Draw the two lines, put the degree marks in and complete the addition as about. We add because a line is 180*(degrees) CORRECT!!!! THEN WE CAN SAY: Angle A + Angle B = 180* Angle B + Angle D = 180* So if Angle A is 100* what is Angle B? Angle A + Angle B = 180* Angle A = 100* 100* + Angle B = 180* SO!!!! Angle B = 180* - 100* Angle B = 80* Right!!! Now...put in your values for your angles and see if they work out that way. Good luck..work..using the concepts outlined..then you will be the MASTER!!