Janice says that the sum of the measures of the interior angles of an octagon is 900°. Is Janice cor

Janice says that the sum of the measures of the interior angles of an octagon is 900°. Is Janice correct? Why or why not?

She's incorrect.
The interior angle sum for a polygon is found with this formula:
Interior Angle Sum = (sides - 2) x 180°

Since an octagon has 8 sides, we have:
Interior Angle Sum = (8 - 2) x 180°
Interior Angle Sum = 6 x 180°
Interior Angle sum = 1080°