Is the answer -1 ? If yes, then here is the solution how. Try to get the equation of the line. Equation of a line is : y=mx + c. Also we know, m , the slope = (diff in y coordinates)/(diff in x coordinates) so, m= (1-2)/(1-1/2) = -2 So line is y=-2x + c now, find c, put x=1/2, y=2, we get c = 3. So...