The diameter of the semicircle is 16 feet.
He calculates that he needs to buy abut 25.12 feet of fencing.
To find amount of fencing we find the circumference of semicircle 
Circumference of semicircle = 
Where d is the diameter of the circle
d= 16 given and value of pi is 3.14
Circumference of semicircle = 
=25.12 + 16 = 41.12 feet
Scott's calculation was wrong because he forgot to add the diameter d
Circumference of circle  is half way of circle plus the diameter of circle.
Correct amount of fencing = 41.12 feet
 
        
             
        
        
        
The sum of exterior angles of a polygon = 360<span>°
Thus, the eighth exterior angle is equal to
360</span>° - (42° + 55° + 39° + 20° + 62° + 45° + 47°) = 50<span>°</span> 
        
                    
             
        
        
        
Answer: 6.4
Step-by-step explanation: If rounding to one decimal place, your answer would be 6.4. 
49.6 divided by 7.8 = 6.35897435...
Now, we see that after the 3 (The first decimal place) there is a five. Because we are rounding to the first decimal place the second decimal place will tell us to round up or down. In this case because it's a five, we would round up.
 
        
             
        
        
        
The answer is -4. I solved it on a calculator and got -4