Since momentum is conserved in the absence of external forces, the total momentum of all the balls after the collision should be equal to the momentum of the cue ball before the collision.
(momentum; is conserved; L:in the absence of external forces) (the total momentum of all the balls; should be; equal to the momentum of the cue ball before the collision; T:after the collision)
momentum the total momentum of all the balls
is conserved should be
L:in the absence of external forces
equal to the momentum of the cue ball before the collision T:after the collision