Using the relation between velocity, distance and time, the equation that relates x and y is given by:
x + y - 3 = 0.
Velocity is distance divided by time, hence:
[tex]v = \frac{d}{t}[/tex]
In this problem, he wants to run 30 km at a rate of 10 km per hour, hence:
[tex]10 = \frac{30}{t}[/tex]
10t = 30
t = 3.
The total time is 3 hours. Considering x as the number of hours he runs and y the number of hours he walks, along with the total time, the equation is given by:
x + y = 3.
In standard form:
x + y - 3 = 0.
More can be learned about the relation between velocity, distance and time at https://brainly.com/question/24316569