Answer:

Step-by-step explanation:
Information we have:
Mass of the sled:

Spring constant:

acceleration of the sled:

We use the formula for the force on a spring (Hooke's Law)

where k is the spring constant and x the distance the mass moved from the equilibrium
and we also use Newton's second Law of motion:

we combine these two equations:

we solve the last equation for the distance x:

and substitute the values:

the negative number means that the mass was moved in the opposite direction that the force, this because the force in a spring is restorative and points towards the equilibrium point