There are three people pushing on a box, as illustrated. Each of the three forces is 45 degrees from the x and y axes (there is no friction between the box and the floor).
Picture of box is attached. The arrows are NOT to scale.
Solution provides equations to find the value and direction of a resultant force, as well as what single force could be added to the box by a fourth person, in order to balance the resultant force. Expert only provides equations.