PLEASE HELP ME WITH THIS QUESTION ILL GIVE BRAINLIEST IF I CAN

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

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.

If f(x) = 5х – 2 and g(x) = 2х + 1, find (f – g)(x).