I primarily work with students in the following suburbs of Chicago:

Libertyville,

Vernon Hills,

Mundelein,

Lake Forest,

Lake Bluff, etc.

Honor's Geometry: Reflections Problem 13.5 #17: Libertyville

Here is the solution. The slope of the "fourth" line is -3/2, so the 2.5 as the y-coordinate of R is not an estimate from the diagram, but actually can be calculated algebraically by writing an equation of that line using two points, and then substituting x=9. But I think in this case it's sufficient to "figure it out" based on slope.

Math and Physics Tutor for High School and College Students in Libertyville, Lake Forest IL, Vernon Hills, etc., and online