How do i solve for x 30x - 60 = 20x i already know x equals 6, but i dont know how to get the answer

In the diagram of circle a what is m

If sr is 4.5cm and tr is 3cm, what is the measure in degrees of angle s?

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