Adding Dungeons and Dragons movement?

I have a player who is an Aarakocra that is a divine soul sorcerer. When they get to level 14 they can gain a flying speed of 30 because they have the divine soul, but they already have a flying speed of 50 because of their race. Would their flying speed by 80 because 30+50? Or would it be 50 because that's the higher of the two?