A bag contains eleven equally sized marbles, which are numbered. 11 numbered marbles are shown. Marbles 2, 6, 7, 8, 10 and 11 are white. Marbles 1, 3, 4, 5, and 9 are shaded purple.

What is the probability that a marble chosen at random is shaded or is labeled with a multiple of 3?

Two-elevenths

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?