25. Find x.

OM is the distance from the center to the tangent point M. OB is the radius. Triangle OMB is a right-angled triangle with the right angle at B (radius to tangent). OB = 15. Angle BOM = 60 degrees. In right triangle OMB, tan(60) = OB/BM. This is incorrect as OM is the hypotenuse. Angle OBM = 90 degrees. Angle BOM = 60 degrees. Angle OMB = 30 degrees. OM = x. OB = 15. sin(60) = OB/OM. sin(60) = 15/x. x = 15 / sin(60) = 15 / (sqrt(3)/2) = 30/sqrt(3) = 10*sqrt(3).