If you are geometrically inclined, like I am, you can visualize the path of the Skoda as a line on a graph where the X axis is the time of day (in military time) and the Y axis is distance traveled in miles.
Here are some points for the Skoda --
(7,0), because at 7 am, the Skoda has traveled 0 miles.
(8,20), because at 8 am, the Skoda has traveled 20 miles.
(12,100), because at 12 pm, the Skoda has traveled 100 miles.
If you plot these points on your graph, you'll see that it makes a straight line with slope 20 and X-intercept of 7. From that you could figure out that the Y intercept is -140.
Similarly, the Porsche would have a slope of 40 and an X-intercept of 16 (we're using military time). From there you could find out that the Y intercept is -640.
So you have
- Skoda's traveled distance = $20*t - 140$
- Porsche traveled distance = $40*t - 640$
We can graph these on a chart --
So you want to know when their traveled distance is equal. So --
$Skoda \, distance = Porsche \, distance$
$20*t - 140 = 40*t - 640$
$20*t = 40*t - 500$
$20*t = 500$
$t = 25$
So, at 25 o' clock, or 1 am the next day, their traveled distances will be the same.