To simplify with exponents, don't feel like you have to work only with, or straight from, the rules for exponents. It is often simpler to work directly from the definition and meaning of exponents. Step-by-step explanation:
When they can no longer afford the mortgage but before they miss a payment.
1. consider one angle of a (convex) heptagon. From that angle you can construct 7-3=4 diagonals. (-3 because we cannot create diagonals with the adjacent vertices and the angle itself )
2. 4 diagonals create 5 triangular regions. (check the picture)
3. So the sum of the measures of the interior angles of the heptagon is 180°*5=900°.
4. The measure of the remaining 7th interior angle is 900°-(120+150+135+170+90+125)°=110°.
5. The largest exterior angle is when the interior angle is the smallest.
6. The smallest interior angle is 90°, so the largest exterior angle is 180°-90°=90°
Answer: 90°