Question on: JAMB Mathematics - 2010

In the diagram above, < STU = < TRS = 25^o

(< between tangent to circle and a circle and a chord through the point of contact = < in the alternate segment)

< RTS = 90^o

(< in a semicircle = 90^o)

x^o + < RTS + < STU = 180^o

x^o + 90^o + 25^o = 180^o

x^o + 115^o = 180^o

x^o = 180^o - 115^o = 65^o