By specifying the variables as the second input to "equationsToMatrix", the conversion will preserve that order. Here is an example:
syms m1 m2 m3 m4 m5 m6 m7 m8 m9 m10 m11 m12
eqns=[m1-m2-m3-m4-m5==0,
m2-m9-m10-m11==0,
m5-m8-m7-m6==0,
m12-m4-m7-m11==0,
m1==100,
m5-5*m8==0,
0.84*m12-m4-m7==0,
0.7*m1-m2-m3==0,
0.55*m1-m9-m12==0,
0.2*m9-m10==0,
0.85*m2-m9-m11==0,
3.2*m6-m7-m8==0];
vars = [m1 m2 m3 m4 m5 m6 m7 m8 m9 m10 m11 m12]; % Specify the variable order here
[A,b]=equationsToMatrix(eqns,vars)
