Final answer:
The net force acting on the box when David pushes it with 11 Newtons to the right and his friend pushes it with 8 Newtons to the left is 3 N to the right.
Step-by-step explanation:
The student's question involves calculating the net force acting on a box when two people apply forces in opposite directions. David pushes the box to the right with a force of 11 Newtons, and his friend pushes the box to the left with a force of 8 Newtons. To determine the net force, you subtract the smaller force from the larger force and keep the direction of the larger force. So, the calculation would be 11 N - 8 N = 3 N to the right. Therefore, the net force acting on the box is 3 N to the right.