You have to give a unique name to each constraint. Multiple assignments are not allowed.
This works on my machine:
/* Variables */
var x{i in 1..3, j in 1..5} >= 0;
/* Objective */
maximize money: 1.04*x[1,5] + 1.09*x[2,4] + 1.15*x[3,3];
/* Restrições */
s.t. c1: x[1,1] + x[2,1] <= 5000;
s.t. c2: x[3,1] = 0;
s.t. c3: x[3,4] = 0;
s.t. c4: x[3,5] = 0;
s.t. c5: x[1,2] + x[2,2] + x[3,2] <= 1.04 * x[1,1];
s.t. c6: x[1,3] + x[2,3] + x[3,3] <= 1.04 * x[1,2] + 1.09 * x[2,1];
s.t. c7: x[1,4] + x[2,4] <= 1.04 * x[1,3] + 1.09 * x[2,2];
s.t. c8: x[1,5] <= 1.04 * x[1,4] + 1.09 * x[2,3] + 1.15 * x[3,2];
/* Resolve */
solve;
/* Results */
printf{j in 1..5}:"\n* %.2f %.2f %2.f \n", x[1,j], x[2,j], x[3,j];
end;
It prints:
* 0.00 5000.00 0
* 0.00 0.00 0
* 0.00 0.00 5450
* 0.00 0.00 0
* 0.00 0.00 0
Good luck!