In science, a velocity in one direction would
be shown as (+) and velocity in the opposite
direction would shown as (-). A baseball
pitcher threw a fastball at a velocity of 42
meters/second. When the batter hit the
ball, it changed velocity to the opposite
direction, moving at 50 meters/second.
According to science, how much did the ball
change velocity when it was hit?

I know that the answer is 92 but idk How it is so can you tell me