If an object has two forces acting on it how can the next force equal 0

If the forces are equal and in opposite directions, the net force will equal zero.

Consider a tug-of-war team. If they are pulling with equal forces against each other, the red cloth on the rope will not move.

F = ma

The cloth is not moving, so a = 0 and the net force F = 0.

1. they vary with a higher number because boiling is way hotter than melting