U first find the common denominator which is 8 
Then subtract to get 7/8
        
             
        
        
        
Area = 10 * 1/2* * 14 * 25  (note decagon has 10 sides)
        =   1750 
        
             
        
        
        
I solved this using a scientific calculator and in radians mode since the given x's is between 0 to 2π. After substitution, the correct pairs
are:
cos(x)tan(x) – ½ = 0
→ π/6 and 5π/6
cos(π/6)tan(π/6) – ½ = 0
cos(5π/6)tan(5π/6) – ½ = 0
 
sec(x)cot(x) + 2 =
0 → 7π/6 and 11π/6
sec(7π/6)cot(7π/6) + 2 = 0
sec(11π/6)cot(11π/6) + 2 = 0
 
sin(x)cot(x) +
1/sqrt2 = 0 → 3π/4 and 5π/4
sin(3π/4)cot(3π/4) + 1/sqrt2 = 0
sin(5π/4)cot(5π/4) + 1/sqrt2 = 0
 
csc(x)tan(x) – 2 = 0 → π/3 and 5π/3
csc(π/3)tan(π/3) – 2 = 0
csc(5π/3)tan(5π/3) – 2 = 0
 
        
                    
             
        
        
        
Answer:
According to logarithmic properties.... The right hand side can be written as 
log base 7 (180/3).....which is log base 7 60
So according to the question cancel out the log base 7 from both sides.... 
Then we get 8r + 20 = 60
That is 8r = 40..
That is r = 5......
Therefore the value of r is 5
 
        
             
        
        
        
You'd first have to find out what percentage of people would be 30 out of 100%