Final answer:
The equation of the line with a slope of 3 and a y-intercept of 9 in slope-intercept form is y = 3x + 9.
Step-by-step explanation:
To write the equation of a line in fully simplified slope-intercept form, we need to identify the slope (m) and the y-intercept (b) from the graph provided or from the given data. The general formula for slope-intercept form is y = mx + b, where m is the slope and b is the y-intercept. In this case, the y-intercept is given as 9, and the slope is given as 3. Therefore, the equation of the line is y = 3x + 9.