The tangent makes a right angle with the diameter at the point of tangency. So, the triangle is a right triangle, and the Pythagorean theorem can be used to find the length of x. The radius is shown as 7.1, so the diameter will be 14.2.
21 students because if 6 represents 30% u add 6 two more time which equals 18 and 90% then u add 3 more because it is half of 6. when u add 3 more u will get 21 and 100%