ten o'clock
`` And did you guess it ? '' `` No , sir , I suddenly recollected what you said . '' `` And pray , what did I say ! '' `` Why , sir , you always said let _ x _ represent the unknown quantity , and -- and _ x _ stands for ten -- ten o'clock . '' Mr Limpney snatched the paper from the boy 's hand , and was about to tear it up , when the door opened and Dr Grayson entered . `` Well , '' he said pleasantly , `` and how are we getting on ? '' `` Getting on , sir ? ''