It is easy.
arcOR=Half of circumference=1/2*18pi=9pi
The original question asks for length of line segment PQ and not the arc. I guess the question meant the opposite.
There is an easier way to find the length of an arc i.e. (theta/360)*2*Pi*r where theta is the angle the arc forms at the center. In this case segment PCQ where c is the center of the circle subtends a angle of 40deg at the center of the circle. Applying it to the above formula, length of the arc is (40/360)*2*pi*9 = 2pi
Calculation of angle PCQ
PC=CR hence CPR=CRP=35deg
PQ ll OR hence QPR=PRO=35 deg
CP = CQ hence CPQ(CPR+RPQ) = PQC=70deg
PEQ = 180-CPQ-PQC = 40deg