Is 2,3-dimethylprop-1-ene a possible organic structure?
2-methylbut-1-ene.

For future reference: an alkyl substituent at the 3 position of a propyl group probably indicates you did not select the longest carbon chain to name the parent molecule.

So your answer was not 'formally' correct.  That being said there was only possible structure to be drawn from the name you used, so correct or otherwise, it is effective communication.