How old are you talking about?
( ( How old ) ( ( ( are you ) ( talking about ) ) ? ) )
(ROOT (SBARQ (WHADJP (WRB How) (JJ old)) (SQ (VBP are) (NP (PRP you)) (VP (VBG talking) (IN about))) (. ?)))
What age do you mean?
( ( What age ) ( ( ( do you ) mean ) ? ) )
(ROOT (SBARQ (WHNP (WDT What) (NN age)) (SQ (VBP do) (NP (PRP you)) (VP (VB mean))) (. ?)))