Answer
See the figure below.
Work Step by Step
Since the object is in equilibrium, the net force exerted on it must be zero.
So that
$$F_x=0 \;\;\;\;{\rm and }\;\;\;\;F_y=0$$
This means that the third force had to be in the negative horizontal direction, as we see below.
Note that all forces start at the black dot in the figure below.