HeY First I'm new to software developing side.
I made some system abount money lending and some my teachers said that system good but there is wrong thing at finding profit/loss page.
Therefore I want your advices guys ! :)
In this system user can register new clients and also their loans.
Another form is there for collect settlments from one who brought loans.
I need to find profit/ loss.
But some clients pay different amounts for there daily settlments.
Then I can't just say this is capital and this is interest income by one settlment.
What should I do to this?

Currently I find profit by below theory:
select two dates using date time pickers and then filter from database one who completed paying loan. And get that loan's full interest income to between that date range.
And like that get amount of expenses between same date range.
then income-expense=profit/loss

Also need your advices and programically practically help :)
Thank You !

More context is necessary before answing the question.
1) What are specification for the assignment?
2) Please post the code you already have for the profit/loss page.
3) Based on this, we may be able to give you some advise, but we will not do your homework for you.

I thought this web was about programming. Your question is more about mathematics.

@Raul: The mathematics forms the basis for the algorithm which would be implemented in the programming language of choice/requirement, so I think it can still be called relevant to the tasks of programming.