I need help on this question i tried it but it told me it is wrong what is the answer

Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

Abag contains 4 red, 7 blue and 5 yellow marbles. event a is defined as drawing a yellow marble on the first draw and event b is defined as drawing a blue marble on the second draw. if two marbles are drawn from the bag, one after the other and not replaced, what is p(b|a) expressed in simplest form? a. 7/16 b. 7/15 c. 14/16 d. 14/15

If there are 3.281 feet in 1 meter, how many inches are in one centimeter