What does an "x" mean in a problem while finding a percent

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.

The computer that controls a bank's automatic teller machine crashes a mean of 0.6 times per day. what is the probability that, in any seven-day week, the computer will crash less than 5 times? round your answer to four decimal places

At school 460 of the students walk to school the number of students who take public transit is 20% of the number of students who walk. how many students take public transit