[Python] Why Do Two Similar Code Snippets Yield Different Results for Symbolic Equations?

I am calculating (what seems to me) the same thing in two ways but am getting different results. I'd appreciate any help in understanding the reason behind this.

I have a list of symbolic equations, each defined as:

a1 * x1 + a2 * x2 + ... + a30 * x30 = b

eqs=[] # expressions
reps={} # values of symbols in the expressions
b=[] # numeric value that the known expression has
for i,e in enumerate(eqs):
A = (e-b).subs(reps)
B = e.subs(reps)-b
if A != B:
print (A, B)


These are giving different results for A and B:



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