A 3 wire dryer circuit is X-Y-N (usually red and black, and always accompanied by white).
Optional grounding may be accomplished by daisy chaining a separate ground wire from the dryer frame to a known ground.
A 4 wire (including ground) dryer plug may not be connected to a 3 wire circuit (without ground).
(One morning on WRKO Radio) The tub's not clean! Let's remodel the bathroom.
(One afternoon on WRKO Radio) It's time for an oil change. I'm going to trade in the car for next year's model.