13. 1
14. 1
15. any number and 0 will have a quotient of 0.
for example 7/0=0 .     8/0=0 .    9/0=0
if you try and check your work using multiplication 7*0=0 .    8*0=0 .    9*0=0
then you will realize the rule is right
        
             
        
        
        
Answer will be: y=7/3+2x/3 
 
        
                    
             
        
        
        
The first five multiples of 9 are 9 18 27 36 45 I hope that's what you mean. 
The prime factors of 9 and 12 are
9: 3 * 3
12: 3 * 2 * 2
The LCM is 3*3*2*2 is 36
The store sold 4 sets of cups ans 3 sets saucers. Answer
 
        
             
        
        
        
7 x 500,000 = 3,500,000.
The towns are 3,500,000 units apart (I don't know what the cm were scale too, sorry.)