Are the following sentence, for two things going on at once, grammatically correct?
- Tom is doing laundry singing a song.
- It is not easy to go to school working part-time.
- I saw an accident riding my bike.
It feels like a conjunction is needed just because I usually don't hear it like that, but I don't know the grammar rules for sure.
edit: I wanted to know because a textbook used sentences like this. They sounded odd, so I wanted to make sure.