Final answer:
For equilibrium to be achieved, Max, the dog, would need to pull with a force of 8 N to the right to counterbalance the 15 N force exerted by Charles to the left.
Step-by-step explanation:
The situation described involves Charles and Maggie in a tug-of-war over a stuffed animal, with Charles pulling to the left with a force of 15 N and Maggie pulling to the right with a force of 7 N. To achieve equilibrium, the forces on both sides must be equal. Since Max joins Maggie and pulls to the right with her, the force that Max needs to exert to balance Charles's force is the difference between Charles's and Maggie's forces, which is 15 N - 7 N = 8 N. Therefore, Max would need to pull with a force of 8 N to the right.