1. The problem statement, all variables and given/known data In a two-dimensional tug-of war, Alex, Betty, and Charles pull horizontally on an automobile tire. The angle between Alex and Betty is 137degrees. The tire remains stationary in spite of the three pulls. Alex pulls with a force of magnitude 220 N, and Charles pulls with a force of magnitude 170 N. Note that the direction of the force applied by Charles is not given. What is the magnitude of force with which Betty pulls? 2. Relevant equations F1 + F2 + F3 = 0 ? 3. The attempt at a solution I do not know how to even approach this problem. Charles could be pulling with Betty, or with Alex, or in some other random direction. What formula could I use that would compensate for Charles?