Question 1036808
Return your attention to the separate functions.


{{{system(r(x)=125x,c(x)=65x+5400,p(x)=r(x)-c(x))}}}
Understand very well what function notation looks like and means.  


Changing from {{{r(x)-c(x)}}}  to {{{(r-c)(x)}}}  is wrong.  Substitute the definition for the two functions and simplify that expression.




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You have the symbolized definitions for the functions r(x) and c(x).  SUBSTITUTE THEM in the expression for p(x).