I have a honda ct90 trail bike

It won't start, there's a tube that leaks gas and I want to know where it is supposed to go

Follow the tube to it's starting point - It could be the overflow from the gas tank - If you can get to the carb spray some starter fluid into it - If it starts for a few sec - You have a gas problem otherwise remove the plug and see it it has gas on it (wet) - If it does - then you have an electrical problem --- Usually the only thing that ever went wrong with the Trail 90 was a bad spark plug.

Need to know where it's coming from as there are two that could be leaking but for different reasons.
Fuel flows from the tank to the carb thru a tube, a float in the carb is supposed to shut that off until throttle is applied and than it lets fuel flow again, like flushing the toilet (hopefully without the turds.
The other line is an overflow, if that float can't stop the flow than fuel will spill into that overflow tube.

So which one is it?

Well it leads to the carberator on top of the engine