It is important that we understand the value of each digit in three-digit numbers.
345 is made up of 300 (3 x a hundred) + 40 (4 x ten) + 5 (5 x one)
673 is made up of 600 + 70 + 3
The value of the 7 is 70 (7 x 10)
Now, let's have a go at writing the value of some digits in three-digit numbers.