(9+d)*8=9*8+d*8 what property is this?

You’re repairing a large rectangular aquarium. the final step is to cover the glass with a protective film. the front and back of the aquarium measure 4 meters by 2 meters, and the sides of the aquarium measure 3 meters by 2 meters. how many square meters of protective film do you need? ( )

Line wx is parallel to line yz. if m

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?