In this question, we have three separate forces. All three forces act at a distance from the pivot point, O. This gives rise to three individual torques, each one caused by a separate force. Note that we have forces acting in different directions, and so may cause different directions of torque. Let's take the forces causing a counter-clockwise motion of the object to have positive torque. Clockwise motions will be taken to have negative torques.

Letting 1 be the torque caused by F1, similarly with 2 and 3, we can see that F1 and F2 both cause torques in the negative direction (ie. clockwise), while F3 causes a positive torque (ie. counter-clockwise). We need to consider this when summing the total torque,  on this object.