90, 45, 45 a right triangle has an angle 90 degree, and the three angles of a triangle make a sum of 180, so the other two angles make up the other 90 degree the right triangle is isosceles, so the other two angles are congruent, of the same degree. Each of them is 45 degree
The 19.485 is the slope of the graph of this equation. This gives the rate of change of the amount of the bill (above $86.912) for each added resident (x).
