Answer:
D
Step-by-step explanation:
 
        
                    
             
        
        
        
It would be A=18 because of the equation a^2+b^2=c^2.
        
             
        
        
        
Do cross multiply or butterfly.  
For example first one.
18/x=6/10  So cross multiply  18×10 =6x
180=6x
Divide both sides by 6 to get x alone
180÷6=30
So x =30  Do the same to rest
 
        
             
        
        
        
90 days.
For this question you just need to find the least common multiple of 18 and 30. That can be found by first finding the prime factorization of each number. 18 = 2 * 3 * 3 and 30 = 2 * 3 * 5. Then you multiply the 2 * 3 * 3 * 5, you ignore the 3 from 30 because 18 has more 3s. The answer is 90.