How can you calculate whether momentum was conserved before and after a collision?

Question

Take the sum of the momentums of both objects before the collision, then take the sum of the momentums of both objects after the collision. If these values are equal, then momentum has been conserved.
Take the sum of the momentums of both objects before the collision, then subtract them from the momentums of both objects after the collision.
Take the sum of the momentums of both objects before the collision, then take the sum of the momentums of both objects after the collision. If these values are not equal, then momentum has been conserved.
Take the sum of the momentums of both objects before the collision, then add them to the momentums of both objects after the collision.

Answer 1

The correct way to calculate whether momentum was conserved before and after a collision is to take the sum of the momentums of both objects before the collision, and then take the sum of the momentums of both objects after the collision. If these values are equal, then momentum has been conserved.