Hi, I am beginner in mathematics , I have the following three relationships:
I need to calculate c under the assumption that a, b and d are known values.
I got c=a-b+d
can I use any other formulas?!!
c=a/b*d is not true.
Unless you mean
That is generally not true but given your conditions...
In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.