We know that, the local/place value of a digit in a number is the value of the digit with reference to its position in that number.
Place value of 3 in the number
3945 is 3×1000=3000
Place value of 5 in the number
3945 is 5×1=5
Diffrence =3945−3000−5=2995
Hence, the difference between the place values of 3 and 5 in the number 3945 is 2995.