The elephant is moving up the ramp at a constant velocity. That means the acceleration is 0. There are forces pulling the elephant up the ramp and forces pulling it down the ramp. Since we know that

NET force = mass*acceleration

and we know acceleration is 0, that means the net force is 0. In other words, the forces pulling the elephant *up* the ramp are exactly equal to the forces pulling the elephant *down* the ramp.

The only force pulling the elephant up the ramp is the 10,000N force provided by Noah and his family.

The forces pulling the elephant down the ramp are 1) the portion of its weight that is directed along the ramp surface, and 2) the frictional force that always opposes any movement on the ramp.

So, if you subtract the forces going down from the forces going up, you should get 0.

10,000N – (elephant’s weight down the ramp) – (frictional force) = 0

Remember that the part of the elephant’s weight that is directed along the ramp takes into account the angle of inclination. Also remember that the frictional force is equal to the coefficient of friction (mu) * the normal force. The normal force is the portion of the elephant’s weight that projects perpendicularly away from the ramp surface. This value also takes into account the angle of inclination of the ramp.

Find the values of the two downward-directed forces and rearrange your balanced force equation to get mu all by itself, and you’ll have your answer!