2. The numbers from 1 to 2019 were written in a row. Which digit was written more: ones or twos, and by how many?
2. Answer. There are 990 more ones. Solution. From 1 to 999, their quantity is the same. From 1000 to 1999, there are 1000 more ones. From 2000 to 2009, there are 10 more twos. From 2010 to 2019, it is the same again. In total, $1000-10=990$.

Grading criteria. Full solution - 7 points. In other cases $-\mathbf{0}$ points.