3. In this century, 200 years will be marked since the birth of the famous Russian mathematician, a native of Kaluga Governorate, Pafnuty Lvovich Chebyshev. Among the numbers that record his year of birth, the sum of the digits in the hundreds and thousands place is three times the sum of the digits in the units and tens place, and the digit in the tens place is greater than the digit in the units place. Determine the year of birth of P.L. Chebyshev, given that he was born and died in the same century and lived for 73 years.
3. Since in the 21st century the 200th anniversary will be marked, the first digit in the number will be -1, and the second will be 8, and the year of birth has the form $18 a c$.

The sum of the digits in the hundreds and thousands place is 9, and it is three times the sum of the digits in the units and tens place ($9: 3=3$ - this is the sum of the digits in the units and tens place). The number 3 can be represented as the sum of two addends in the following way:

$$
3=0+3=1+2 \text {. }
$$

From this, we can conclude that the digits in the tens and units can be 3 and 0, 1 and 2. Thus, the year of his birth can be $1803, 1812, 1821, 1830$. Since the digit in the tens place is greater than the digit in the units place, only two dates remain: 1821 and 1830. The latter year does not satisfy the condition that he was born and died in the same century $(1830+73=1903)$.

Answer: 1821.