A girl and boy pull in opposite directions on a stuffed animal. The girl exerts a force of 3.5 N. The mass of the stuffed animal is 0.2 kg, and it is accelerating to the right 2.5 m/s2.

What is the force that the boy is exerting? N

I'm gonna have to assume the girl is on the right side and boy on left.

The net force is the sum of all forces on an object (includes negatives).

Let's say the force of the boy is variable b. Use the formula F = ma.

b + 3.5 = 0.2 (2.5)

This is now simple algebra. Solve to get that the boty is exerting a force of - 3N to the left.