Steps to solve:
0.3x = 15
~Divide 0.3 to both sides
0.3x/0.3 = 15/0.3
~Simplify
x = 50
This is a vertical line so the slope is undefined. 
The line passes through the point (50, 0) and there is no y-intercept since its a straight vertical line.
Best of Luck!
 
        
             
        
        
        
The answer you're looking for is A
        
             
        
        
        
-- After dog ate 1/2 of the collection, there were 29 remaining.
-- Just before dog came along, there were (2 x 29) = 58 cards.
-- That was after Dan added 5 new ones.
-- Before he added the 5 new ones, there were (58 - 5) = 53 cards. 
-- When this story began, Dan had <em>53 cards</em>.
        
                    
             
        
        
        
The greatest common factor is 6
36: 1, 2, 3, 4, 6, 9, 12, 18, 36
42: 1, 2, 3, 6, 7, 14, 21, 42
Hope this helps : )