In chemistry class 18 liters of 30% alcohol solution must be mixed with 20% solution to get 14% solution how many liters of 20% solution are needed?

Abird on top of a 200 ft bridge tower sees a man standing on the lower part of the bridge (which is 50 ft above the ground). the angle of depression from the bird is 26 ̊. how far is the man from the base of the bridge tower? with explanation and pictures .