How does the game calculate attack speeds slows basically. For instance if Nid healed and ally and Malphite used his aoe attack speed slow how do they get applied.
All debuffs stack multiplicatively, so they will never reach 100%. For instance, you can't stack slows on the same target to make it into an immobilize or root: slow 100%. If you slow a target by 55% then a teammate slows the same target by 35% (Zilean slow with Ashe auto attack), the target will move at 45% movement speed from Zilean. This new movement speed will be reduced by 35%. So effectively, your movement speed would be 0.45*0.65 or 29.25% of your original movement speed.
Attack speed reductions stack multiplicatively, and take percentages off the final attack speed value after all bonus attack speed has been factored in.