Answer:
5:40
Step-by-step explanation:
This is a problem involving the least common difference.
If you know that the red and blue trains left at the same time at 5, you know that another red train will leave at 5:08. Another blue train at 5:10.
The way to solve this will be to write out the factors of 8 and 10 and find the smallest number that they overlap.
Red:
8, 16, 24, 32, 40, 48, 56, 64, 72, 80
Blue:
10, 20, 30, 40
You see that after 40 mnutes, they are both leaving the station again. After 40 minutes, at 5:40, they are both leaving.
Um.. Both of those equations are the exact same. Divide both sides of the first equation by 6. You get:

That is the exact same as the second equation. This system has an infinite number of solutions. 5x - 7y = -1 is a line, so basically every point on that line is a solution to the system.
For example,

and

would work, but so would

and
Mult 2 by x you'll get 2x then 2 by 3 you'll get 6 and add 6 to 5, after that you'll get 11 it should look like this 2x+11.
7q^2 - 28 = 0
7q^2 = 28
q^2 = 4
q = +/-2
solution set is {-2,2}