If f(x) = 7(x-1)+8, what is the value of f(1)

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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.

y=2x−1 5x−4y=1 is (1,1)(1,1) a solution of the system?