Question

What is the slope of a line passing through (5, 9) and (7, 15)?

Answer 1

We know that 
slope of a line is given by y2-y1/x2-x1
so 
put the values here 
we get 
m=15-9/7-5 
  => 6/2
 => slope = 3 

Answer 2

We know that

x2 - x1 / y2 - y1

putting the value of this formula

= 7 - 5 / 15 - 9

= 2/6

= 1/3