Answer:
5 N
Step-by-step explanation:
Goofy is blocking the way with 15 N force and Donald was only able to knock Goofy off using a 20 N force. The net force would be the difference between the applied force of Donald and that of Goofy.
Hence,
20 N - 15 N = 5 N
The net force is, therefore, 5 N.