Problem 9. Find the smallest number such that when divided by 2018, the remainder is 2017, when divided by 2019, the remainder is 2018, and when divided by 2020, the remainder is 1.
Answer: 4074341

Problem 10. Solve the equation

$20\{x\}-18[x]=0$, where $[x]$ denotes the integer part of the number $x$, i.e., the greatest integer not exceeding $x$; $\{x\}$ denotes the fractional part of the number $x$, i.e., $\{x\}=x-[x]$. Write the sum of the roots in the answer.

Answer: 1.9