can anybody help me with this pleaasssse :((((

Remember there are two forces in action: the man pushing the block horizontally and 2. an opposite force acting against it. The acceleration is the result of the difference of these two forces.

   Step one: find the force of the Friction: what is the Normal force (that is your wieght due to gravity) of the crate and multiply that by the coefficient of friction. Ff=UkN

then take the force for the man 475N then subtract the friction force.

Once that is done you still have to find the acceleration. Hint F=ma

This is only a hint, the numbers you need to fill in. I hope this clears it up without giving you the answer.