Find the gradient of the line on which the points (1,3) and (3,4) lie and find the y-coordinate of the line at x = 7.

The gradient is m = (y1-y0)/(x1-x0) = (4-3)/(3-1) = 1/2. So the equation of the line is y= x/2 + c where c is a constant. To find the constant, c, we will input one of the given coordinates (1,3). This shows 3 = 1/2 + c, so c= 5/2 or 2.5. Therefore, the equation of this line is y = x/2 + 5/2. So, when x=7, y = 7/2 + 5/2 = 6.