Numbers expressed using exponents are called base :)
        
             
        
        
        
Step-by-step explanation:
the formula to calculate a circumference is 

(consider x as the diameter)
so I'll be noting the circumference as C alongside the circle's ranking
a.

b.

c.

hope I helped
 
        
             
        
        
        
Jackson used 8/9 of a case of soda to fill 1/3 of the soda machine.
how many cases does it take to fill the soda machine = ?
1/3 means three parts of the soda machine, it means if we fill with 8/9 of a case three times soda machine will be full so,
8/9 + 8/9 + 8/9 = 24/9 
it means it takes the case of soda between 2 and 3.
2.667 approx. cases of soda it take to fill the soda machine.