The equation is just work done, #w = F xx s# provided the force applied is in the direction of the displacement, s. So if a workman pulls a tool 0.5m towards him with a force of 8N the work done is: #w = F xx s = 8 xx 0.5 = 4 Nm# Just be careful to use distance in m even if it is quoted in cm or km in the question.

At a higher level, we introduce the idea that the force could be at an angle to the displacement (e.g. a dog pulling it’s owner on a lead), in which case we use #w = F xx s xx cos theta# where #theta# is the angle between them. This means no work is done if the force is a right angles to the displacement travelled.