What is meant by zero principal

Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

How many kilometers are equal to 5 miles? use 1 mile ≈ 1.61 kilometers. !

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