## TPTP Problem File: ROB013-1.p

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```%--------------------------------------------------------------------------
% File     : ROB013-1 : TPTP v7.5.0. Released v1.0.0.
% Domain   : Robbins Algebra
% Problem  : If -(a + b) = c then -(c + -(-b + a)) = a
% Version  : [Win90] (equality) axioms.
% English  :

% Refs     : [Win90] Winker (1990), Robbins Algebra: Conditions that make a
% Source   : [Win90]
% Names    : Lemma 3.5 [Win90]

% Status   : Unsatisfiable
% Rating   : 0.00 v7.4.0, 0.04 v7.3.0, 0.00 v7.0.0, 0.05 v6.3.0, 0.00 v6.0.0, 0.05 v5.5.0, 0.00 v2.0.0
% Syntax   : Number of clauses     :    5 (   0 non-Horn;   5 unit;   2 RR)
%            Number of atoms       :    5 (   5 equality)
%            Maximal clause size   :    1 (   1 average)
%            Number of predicates  :    1 (   0 propositional; 2-2 arity)
%            Number of functors    :    5 (   3 constant; 0-2 arity)
%            Number of variables   :    7 (   0 singleton)
%            Maximal term depth    :    6 (   3 average)
% SPC      : CNF_UNS_RFO_PEQ_UEQ