1. Calculate the total number of degrees in octagon. The formula is (Number of sides – 2)*180 or 6 times 180 = 1,080. Actually you can skip this step.

2. Draw lines through each of the opposite corners (all 4 lines crossing through the center of the octagon. That gives you 8 identical isosceles triangles. Now since a circle has 360 degrees the angle opposite to the base and between the two equal sides is 360/8 = 45. Therefore, you know the other two angles are (180-45)/2 = 62.5

3. By law of sins we know 9/sin45 = s/sin62.5 so the equal sides s = 9*sin62.5/sin45. I’ll let you calculate.

4. The area of the triangle is 0.5ab*sinC. Therefore the area of the octagon is 8(0.5s*s*sin45) or 4s^2sin45. You do the calculation.

The next problem is much easier. Since the 15 m line goes from the center of the pentagon to the center of one side, drawing lines from the center of the pentagon to the center of each side and to each corner you create ten identical triangles (1) from the center of the pentagon to the center of one of the bases (2) to the corner of the base (3) back to the center of the pentagon. One angle is of each of the ten triangles is 90 degrees, the angle at the center of the pentagon is 360/10 =36.

Now calculate half the length of a side of the pentagon (b/2) = 15*tan36 Therefore each side b = 30tan36.. You do the calculation. The area of a triangle is 0.5bh with h=15 meters. The pentagon has 5 bases so area of the pentagon is 5(0.5bh) or 2.5*15b meters squared. You do the calculation. It should be between 800 and 900 sq meters.

The second one requires trigonometry and I’m not into that anymore.