Answer:
a) 
b) 
Step-by-step explanation:
Number of balls in the urn = 12
Number of white balls in the urn = 4
So, number of balls which are not white = 12 - 4 = 8
We know that probability = No. of outcomes/Total number of outcomes
Let
denotes the event of getting white ball by A, B and C
a) each ball is replaced after being drawn.
Probability = Number of white balls/Total number of balls
Solution: 
b)the balls that are withdrawn are not replaced.
Solution:
If A wins: 
If A lost and B wins: 
If A and B lost and C wins: 
and so on....
If an is 18 and as is half its length it would be 9, AD = 9

Step-by-step explanation:
The ratio cosine tell us that
- In a right angled triangle, the cosine of an angle is the side adjacent to the angle divided by the hypotenuse of the triangle.
In other words,

The side adjacent to angle a is 9. The hypotenuse is 41.
So
