The slope of the line can be calculated by finding the change in y divided by the change in x between any two points on the line. Let's use the points (0,12) and (6,18) to calculate the slope:
Slope (m) = (y2 - y1) / (x2 - x1)
Slope = (18 - 12) / (6 - 0)
Slope = 6 / 6
Slope = 1
Now that we have the slope, we can use the point-slope form of the equation of a line to write the equation of the trend line:
y - y1 = m(x - x1)
y - 12 = 1(x - 0)
y - 12 = x
y = x + 12
Therefore, the equation of the trend line in slope-intercept form is y = x + 12.