This is algebra and too blurry to see. for 12 you have
4/3x-1/2x=-5 so 8x-3x/6=-5 and 5x/6=-5 so x=-6
3) Definition of a parallelogram
4) Alternate interior angles
5) Reflexive property
6) ASA property
Please say if I got anything wrong!
Your ratio of miniDVD to standard DVD is 2/7