Watt worked as a mathematical-instrument maker from the age of 19.
1 Did Watt work as a mathematical-instrument maker?
2 Who worked as a mathematical-instrument maker from the age of 19?
3 Did Watt work as a mathematical-instrument maker from the age of 19 or 21?
4 Watt worked as a mathematical-instrument maker, didn't he?
5 From what age did Watt work as a mathematical-instrument maker?