Firstly, all sides of a regular octagon are equal, thus, the angles would be too. Since each exterior angle is supplementary to the the interior angle, in total it would be 180 degrees. We know that the sum of the angles would have to be 1080 degrees, so we only have to divide by 8.
3% is the interest so you would do 3% of the investment plus the original investment so 3%×I=z and then z+I=the answer. sorry if this didnt help I'm new and I tried my best sorry!
