Ok, I solved the question posed in the attached image. I did so by using the car's center of mass as the location of my axis of rotation, generated torque and force equilibrium equations, and solved for all unknowns. When I try to use another location for my axis of rotation, e.g., the point where the front wheels make contact with the ground (thus eliminating the friction forces since their torque arm=0), I get an answer straight away -- but it's not correct! My experience -- plus my textbooks (Halliday & Serway) -- say selecting any arbitrary location for my axis of rotation is valid (whether you have enough equations to cover the unknowns is a different matter). QUESTION: It seems, in this case, the choice is not arbitrary: I must use the COM as the axis of rotation location. WHY? Does it have something to do with the car not being in x-dimension equilibrium?