Can someone tell me how to solve numbers 3,4,5, and 6 please.

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

Deshawn uses 3/4 of a box of rice to cook dinner the portion he uses weighs 12 ounces right and solve an equation to find the weight of the full box of rice

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 .