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.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.