The measure of an exterior angle of a regular polygon is 72 degrees. find the measure of an interior angle.

Really need on these. i have no idea what to do

Create and solve a linear equation that represents the model, where squares and triangles are shown evenly balanced on a balance beam. assume the weight of a square is 1 unit and the weight of a triangle is unknown.

How many triangles can be drawn with side lengths 4 centimeters, 4.5 centimeters, and 9 centimeters? explain