An 80 kilogram skier slides on waxed skis along a horizontal surface of snow at a constant velocity while pushing with his poles. what is the horizontal component of the force pushing him forward?

From Newton's First law, if velocity is constant than the net force on the body is zero; or net force in horizontal direction is zero and net force in vertical direction is also zero.

If we assume that the there is negligible friction between waxed skies and snow, than there will be no frictional force on skies in horizontal direction and as net force in horizontal direction is zero, hence the horizontal component of the force pushing him forward is also zero.

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards