T(r+4)=28 solve for t

pls help

Find the measure of the interior angles of the following regular polygons: a triangle, a quadrilateral, a pentagon, an octagon, a decagon, a 30-gon, a 50-gon, and a 100-gon.

How is working backward similar to solving an equation?

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs