how do I find the missing legnth of a polygon it has 16 and 28 on one polygon and 20 and 20 on the other and I have to find the missing side what is the answer

Simplify the expression. -2/5(10+15m-20n)

Lucy and donavan measured the length of the school garden. lucys measurement is 11.3m and donavans measurement is 113 cm. could both be correct? explain

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.