Write the numeral before and after. 16 18 19

The numeral before 16 is $16 - 1 = 15$.
The numeral after 16 is $16 + 1 = 17$.
So, for 16, the answer is $\boxed{15 \quad 16 \quad 17}$.

The numeral before 18 is $18 - 1 = 17$.
The numeral after 18 is $18 + 1 = 19$.
So, for 18, the answer is $\boxed{17 \quad 18 \quad 19}$.

The numeral before 19 is $19 - 1 = 18$.
The numeral after 19 is $19 + 1 = 20$.
So, for 19, the answer is $\boxed{18 \quad 19 \quad 20}$.

Here are the complete answers:
For 16: $\boxed{15 \quad 16 \quad 17}$
For 18: $\boxed{17 \quad 18 \quad 19}$
For 19: $\boxed{18 \quad 19 \quad 20}$