If Frankie the kangaroo climbed out of the crate and pushed the crate with a mighty 12 newtons of force against the efforts of Fred and the man (each applying 10 newtons of force), what would be the net force on the crate from all the pushing?

Answer 1

That depends upon whatever force "Fred" is applying. You seem to have omitted part of the problem.

Answer 2

If Frankie the kangaroo climbed out of the crate and pushed the crate with a mighty 12 newtons of force against the efforts of Fred and the man (each applying 10 newtons of force), what would be the net force on the crate from all the pushing?