The sum of the measures of seven angles of an octagon is 1000 degrees fine the measure of the eighth angle

now, we're assuming this is for interior angles.

the sum of all the interior angles in a polygon is

180(n - 2)   n = number of sides in a polygon.

now, this is an OCTAgon, it has OCTA=8 sides, so it has a sum of its interior angles at 180( 8 - 2) --> 180(6) ---> 1080°.

now, we already know seven of those eight angles add up to 1000, so... surely you'd know what the last one is.