Answer:
the circumference of the dics is 62.8cm
Step-by-step explanation:
 
        
             
        
        
        
        
1*n-10 = (5/6)*n-((1/3)*n)-7 // - (5/6)*n-((1/3)*n)-7
1*n-((5/6)*n)+(1/3)*n-10+7 = 0
n+(-5/6)*n+(1/3)*n-10+7 = 0
1/2*n-3 = 0 // + 3
1/2*n = 3 // : 1/2
n = 3/1/2
n = 6
That's just in case you had to show your work lol^^
        
                    
             
        
        
        
Answer: V=πr^2h=π·4^2·8≈402.12386cm^2