[R] need suggestion about building formual

[Simple]

hi,
I'm an newbie for R,I want do some fitting in R.

I wander if it is possible to write a few of equations but only one formual 
when fitting 

Currently,My problem is,in R, is there methods combination a few equations 
into one formual?
For example, 
y=f1(k);
k=f2(t);
t=f3(x);
although it is certain that the can be equations turn into one formual as 
y~f(x),but write such a complexity string make me painful.

I have searched the web and found out there were only examples with one 
formual.any suggestion? 

I hope that I have omit something.