Well, if the aircraft is in flight, this means that the lift of the wing must equal the weights of the two engines, the wing, and half of the body of the plane assuming that the other wing supports the other half of the body. So the reaction at the left part of the wing is the weight of the plane pulling down.
One can find that force by integrating the lift along the wing and subtracting the weights of wing and engines. The weight of the wing is uniformly distributed. The weights of the body and engines can be treated as point loads.
The right side is free, the left side is constrained by the body, so think about cantilever beam boundary conditions.