Answer with explanation:
Equation of line Passing through two points (a,b) and (c,d) is given by:
          
Equation of line Passing through two points (8,0) and (3,7) is given by: 
       
Comparing with slope intercept form of line, 
y= m x+c, where , m is slope and c is y intercept.
⇒Y intercept = 11.2
Equation of line Passing through two points (5,5) and (3,7) is given by: 
             
Comparing with slope intercept form of line, 
y= m x+c, where , m is slope and c is y intercept.
⇒Y intercept = 10
Equation of line is, y= -x +10.