A force did 80 j of work on an object in 4 m how big was the force

Work = (force) x (distance)

80 J = (force) x (4 m)

Force = (80 J) / (4 m) = 20 N

That's IF the force was in the same direction as the 4m of motion.

If the force was kind of slanted, then it had to be stronger, and

it had a component of 20N in the direction of the motion.