Retrieving an implicit solution


I am building an activity around average rate of change to estimate when a car will finish a race. To find the exact value, I want to use calculus in the background. I have a way for checking any of the simpler problems (constant or linear velocity function using Quadratic Formula). However, ideally the velocity function could be any function and I want to find the first root of its position function. Desmos solves these implicitly, but there is no way to retrieve the value that I can think of.

link to sketch