Delayed goals

/*How do I overcome the 
delayed goals in this code, to
get the desired result 
X=130, Y =70, Z = 80?

Doug Edmunds
16 Dec 1999
*/


:=lib(fd).

g :- X #>0, Y#>0, Z #>0,
X + Y + Z #= 280,
X #= 130,
Y #= Z - 10.


Additional comment:

I added a line
indomain(Y), 
at the end, and it produces the correct answer.

Q: Is there a more efficient way to handle this?