Middle Grades Geometry Arithmetic Sequence

Question

a, b, c, d, e, f, g, h, i are measures of nine angles of a nine-sided polygon. a, b, c, d, e, f, g, h, i is an arithmetic sequence, and c = 130 deg. Find the measure of the largest angle. 

Answer 1

a₁ + 2d = 130

a₁ + 9d = 1260

Subtract top from bottom, solve for d, and determine h.