they say anglePAB=60 which means the two vectors which we'll use are AP and AB
AP=OP-OA and AB=OB-OA
then apply scaler product, ull reach to -3(t+1)=[rootof (6t^2+8t+10)][1/root2] , square both sides and simplify ull get 3t^2+7t+2=0
to get the only position vector of P, u solve this equation, ull get t=-2 and t=-1/3, t=-1/3 is rejected since itll give u obtuse, whereas we have 60 degrees, so substitute t=-2 in OP ull get teh only position vector of P.