If two pipes function simultaneously, the reservoir will be filled in 12 hours. One pipe fills the empty reservoir 10 hours faster than the other. How many hours does it take the second pipe to fill the reservoir ?

In the given figure, O is the center of the circumcircle of triangle XYZ. Tangents at points X and Y intersect at point T. If angle XTY = 80° and angle XOZ = 140°, find the angle ZXY.

Using assumed mean method, calculate the mean.