Hello, xXxSANJIxXx!

The Captain had the best solution . . . direct and simple.

Here's a baby-talk approach.

(It's not as efficient, but it has worked for me many times.)

A tourist bus leaves Townsville and heads North at an average speed of 50 kph.

It does not stop until it reaches the small and little known settlement of Goanna Creek.

A second tourist bus leaves Townsville 2 hours later than the first and travels at 70 kph.

The second bus arrives at Goanna Creek at the same time as the first bus.

How far is Goanna Creek from Townsville?

Bus $\displaystyle A$ had a two-hour headstart . . . it has already gone 100 km. Code:

: - - 100 - - : - - - 50t - - - :
Bus A T-------------+-----------------G
Bus B T-------------------------------G
: - - - - - 70t - - - - - - - :

During the next $\displaystyle t$ hours, bus A travels $\displaystyle 50t$ km and reaches Goanna Creek.

During the same $\displaystyle t$ hours, bus B travels $\displaystyle 70t$ km, the entire distance.

Since their distances are equal: .$\displaystyle 70t\:=\:50t + 100\quad\Rightarrow\quad t = 5$ hours.

So bus B drove for 5 hours at 70 kph . . . the distance is: $\displaystyle \boxed{350\text{ km}}$