How can I play my Android phone's audio directly into my Yaris's basic audio system?

[yotoya]

I recently bought an 2008 Yaris. It comes with an audio system that looks like this



It comes with a CD slot, FM and AM. But it can't play the stuff from my Android smartphone. What are the options to make use of the car's speakers?
I prefer an inexpensive solution.

I understand I can buy an FM transmitter. But perhaps it would be better if there was some way to connect the smartphone to the audio system by a line. Is there something at the back of the audio system that lets me connect it directly? I think the audio would be much better than by FM transmitter.