7.1. Find the number of three-digit numbers for which the second digit is less than the third by 3.
7.1. The first digit of the number can be chosen in 9 ways (it can be any digit from 1 to 9), the second digit in 7 ways (it can be any digit from 0 to 6), and the third digit is uniquely determined. We get $9 \cdot 7 \cdot 1=63$ three-digit numbers that satisfy the condition of the problem.

Answer: 63