What is the underlying complexity decimal numbers were used to represent

If we are talking about computer science:

The decimal numbers are the numbers that we use every-day (0, 1, 2, 3, 4,  5, 6, 7, 8, 9)

The use of these "symbols" facilitates a lot of things because the decimal numbers are easier to read and use than the binary system, so the "underlying complexity decimal numbers were used to represent" are the bits.

answer: the net deposit amount   (option c)

in order to fill in the deposit slip, michael needs to fill in the amount that he wants to deposit in the bank. without the net deposit amount, he will not be able to deposit the money because it is mandatory for him to mention it, as the bank needs to maintain a record to avoid any inconveniences for the bank and michael in the future.

the bank officer checks and verifies the amount received against the amount written on the deposit slip to process the slip.