In 
this question we are asked about a tug of
war competition between two schools: St Benedict's
and St Arthur's. By considering the forces
on the rope we can write down an equation
in terms of x, y, A and B. Since neither team
is winning in this competition we know that
the rope must be stationary. That means that
it must be in equilibrium and thus the resultant
force on it must be zero. This means that
the force exerted by St Arthur's team must
be equal and opposite to the force exerted
by St Benedict's team. The total force exerted
by St Arthur's is x, the number of St Arthur's
competitors, multiplied by A, the average
force each of them will exert. In a similar
way the total force exerted by St Benedict's
team is y, the number of competitors they
have, multiplied by B, the average force that
each of them exerts. These two forces must
be equal and opposite. We can now form an
equation containing x, y, A and B.
