Understanding the order of unification in a given query

Clash Royale CLAN TAG#URR8PPPUnderstanding the order of unification in a given query
Consider the following query ?- B=A+1, A=C, C=B-1.
?- B=A+1, A=C, C=B-1
Prolog, in this case, outputs :
B=B-1+1,
A=C, C=B-1.
Why is that? i would expect C = B-1+1-1 or C = A + 1 -1.
What is the order of he unification? how prolog deals with such query?
C = B-1+1-1
C = A + 1 -1
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