We know that they have:
2 entrences
3 ways to chose (escalator,elevator and stairs)
8 gates
and again 3 ways to chose (escalator, elevator and stairway)
now you have to multiply it:

There are 144 different ways that Anita and Terry can go from street level to the trains:)
Answer:
-3+13x=9.
13x=9+3
13x=12
x=12/13
i proved it by putting value of x in reactant side you get product .
-3+13×12/13=9
hope this helps-------------