The answer to this question is b
        
                    
             
        
        
        
Answer: x = 20
We know opposite angles are equivalent so we can set both of these expressions equal to each other to solve for x. 
3x + 50 = 6x - 10
50 = 3x - 10 (subtract 3x from both sides)
60 = 3x (add 10 to both sides)
20 = x (divide both sides by 3)
 
        
        
        
The two lines are parallel, therefor 90-28=internal angle=62. Using trigonometry, Cosine=a/h. Cos(62)=350/x. Rearrange to get 350/Cos(62) = 519.7(1dp)