Question 1205470
Meaningless until you know the content of copper in the brass!
You need to look into this so you can ultimately find a result.


4parts + 3parts = 7 total parts.


Your brass itself will be some fraction copper.  A basic expression for amount of copper in your alloy is this:


{{{(4*f+3)/7}}}, using f as the fraction of your BRASS which is copper.  Go onward from there.