Final answer:
The slope of the part of the roof represented by the triangle on the graph is 3.
Step-by-step explanation:
The slope of a line represents the steepness of the line. In Figure A1, the slope is given as 3, which means there is a rise of 3 on the vertical axis for every increase of 1 on the horizontal axis. So, the slope of the part of the roof represented by the triangle on the graph would also be 3, as it lies on the same straight line.