Question 840509
Solution : 
Consider the first equation as 2y-6bx = 7
Write this equation in the slope intercept form 
y = mx + b where m is the slope , 
2y - 6bx = 7 
Adding 6bx on both the sides , 
2y = 6bx + 7
Divide by 2 on both the sides , 
y = 3bx + 7/2
So here comparing with the y=mx + b , 
  m1 = 3b
Similarly the second equation 5y+30x+13 = 0 
subtract the 30x and 13 from both the sides we get , 
    5y = -30x - 13 
Divide both the sides by 5 
   y = -6x - 13/5
So by comparing m2 = -6 
Now it says that the slopes of the lines are equal
  m1 = m2 
  3b = -6 
 b = -2 

Thank you .