I have this code:

eq1 = 4 x1 + 5 x2 - 9 x11 == 5;
eq2 = 5 x1 - 3 x2 + 3 x11 == 99;
eq3 = 2 x1 + 5 x2 - 4 x11 == 7;
system = {eq1, eq2, eq3};
solution = Solve[system]

and the output is:

{{x1 -> 2574/161, x11 -> 1094/161, x2 -> 71/161}}

I would like the output to go in order i.e. x1, x2, and then x11, but I cannot figure out how.

  • Use x[1],x[2],x[1,1] (or x[1],x[2],x[11]) instead of x1,x2,x11. – AccidentalFourierTransform Nov 13 at 2:17
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  • BTW, you can even suppress the output of x11 by using Solve[system, {x1, x2}, {x11}], if you want to. – Αλέξανδρος Ζεγγ Nov 13 at 7:06
up vote 12 down vote accepted

Solve will return the solutions in the order requested:

solution = Solve[system, {x1, x2, x11}]
(*  {{x1 -> 2574/161, x2 -> 71/161, x11 -> 1094/161}}  *)
SortBy[#, {StringLength @ SymbolName[#[[1]]] &}] & /@ solution 

{{x1 -> 2574/161, x2 -> 71/161, x11 -> 1094/161}}

Try also this:

solution /. {a_, b_, c_} -> {a, c, b}

(*  {{x1 -> 2574/161, x2 -> 71/161, x11 -> 1094/161}}   *)

Have fun!

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