Answer:
Step-by-step explanation:
every time x goes up 1,  y goes up 4   
x = 3  minus x = 2  is a delta (a change of 1)
x = 4  minus x = 3  is a delta (a change of 1)
x = 5  minus x = 4  is a delta (a change of 1)
        the delta x is ALWAYS 1 for this table you can always substract x's to find the delta     delta is symbolized by Δ      Δx  for the delta x
y = 7  minus y = 3  is a delta (a change of 4)
y = 11  minus y = 7  is a delta (a change of 4)
y = 15  minus y = 11  is a delta (a change of 4)
     the delta y is ALWAYS 4 for this table you can always substract y's to find the delta     delta is symbolized by Δ     Δy  for the delta y
the slope m = Δy / Δx      m = 4 / 1     m = 4
      y = mx + b             when x = 0    then  y = b   (called the y intercept)
so how do we find the y intercept?     
look at the pattern in the TABLE  Δx  and Δy
    when x = 1    y = (3 - 4)  = -1
              x = 0    y =( -1 - 4)   = -5
so       y = 4x - 5     is a line equation for the data in this table
                                 I believe there are other forms for linear equations
                                I chose the y-intercept form
 use the point slope equation 
        (y - y1)  =  m(x - x1)            where (x1, y1)  are the coordinates of a point on  
                                                 the line 
        when you know the slope of the line and a point on the line
        as before
        m = (y2 - y1)  / (x2 - x1)          from the table
            = (7 - 3) / (3 - 2)                 still equals
            = 4/1  =  4         
         pick a point on the line    say x= 4 and y = 11    (4, 11)
        (y - y1)  =  m(x - x1)    
         y - 11   =   4(x - 4)              point slope form
 
          solving point slope form  for  y
         y  - 11  =   4x - 16               add 11 to both sides     
            y  =  4x - 5                     back to the y-intercept form