Answer
See the graph below.
Work Step by Step
The author here asks not to solve the problem or do any math, he just needs the drawing. We just need to sketch the problem. And here we go...
Noting that "steady declaration" means the speed of the motorist decreases at a constant rate which means at a constant acceleration.
Also, note that $d$ is the distance traveled during the reaction time $\Delta t=0.5\;\rm s$ while $\Delta x$ is the distance traveled from the start of braking to the complete stop at the stoplight.
