Find the place value and face value of 5 in 9,851,086,083. Also, find the difference between them.

The digit 5 is in the hundred millions place.

Place value of $5 = 5 \times 100,000,000 = 500,000,000$.
The place value of 5 is $\boxed{500,000,000}$.

Place value = 500,000,000
Face value = 5

The difference is $\boxed{499,999,995}$.

12. b) Find the sum and difference between the place values of two sevens in the number 6784037525.

The first '7' is in the hundred millions place.
Place value of first $7 = 7 \times 100,000,000 = 700,000,000$.

The second '7' is in the thousands place.
Place value of second $7 = 7 \times 1,000 = 7,000$.

The sum is $\boxed{700,007,000}$.

The difference is $\boxed{699,993,000}$.

12. c) Find the sum and difference between the place values of nine in the numbers 49560327 and 1024968.

The '9' is in the millions place.
Place value of '9' in $49,560,327 = 9 \times 1,000,000 = 9,000,000$.

The '9' is in the hundreds place.
Place value of '9' in $1,024,968 = 9 \times 100 = 900$.

The sum is $\boxed{9,000,900}$.

The difference is $\boxed{8,999,100}$.