Wat must be subtracted from 3/4 to give 1/2

Lola says these two expressions have the same value. expression a expression b which explains whether lola is correct?

If a is a nonzero real number then the reciprocal of a is

From the top of a tree a bird looks down on a field mouse at an angle of depression of 50°. if the field mouse is 40 meters from the base of the tree, find the vertical distance from the ground to the bird's eyes.