yet another AS physics question, please help!!!?

Question

A tractor sits on a bridge supported by two posts A and B. THe back wheel exerts a force of 14.000N and the front 6,000N. Calculate the force on each support.

distance from A to back= 5m
distance from BAck to Front= 3m
Distance between A and B= 15m

Answer 1

You forgot to specify which direction the tractor is facing. For if the tractor faces B, the distance from A to front = 8m, otherwise the distance from A to front = 2m.

Let us assume that the tractor faces B, so that the distance from A to front = 8m.
Of course both A and B are the support points. Let the force on B to be xN. That means B "pushes up" with xN. You can also "imagine" that there is no rotation around A (or B), so the net toque around A is zero:
5*14000 + 8*6000 - 15*x = 0
x = (5*14000 + 8*6000)/15 ≈ 7867(N)
that is the force on B. Hence the force on A is 20000N - 7867N = 12133N.
You may check this by considering B as the rotational center.