Answer: 225 joules.
Step-by-step explanation:
If this a one dimension problem, this is the motion is in the same direction of the force, the equation for work is:
Work = distance × force
⇒ Work = 15 m × 15 N = 225 joules.
This is a special case of the general equation
Work = |F| |displacement| cosine (angle between the force and displacement)
When force and displacement are in the same direction, the angle is 0, so cos(0) = 1. This is the two vectors are parellel and the work is just the product of the two magnitudes (force and distance)