let GF be non empty right_complementable well-unital distributive Abelian add-associative right_zeroed associative doubleLoopStr ; :: thesis: for V being non empty right_complementable vector-distributive scalar-distributive scalar-associative scalar-unital Abelian add-associative right_zeroed ModuleStr over GF
for u, v being Element of V
for W being Subspace of V st v + W = u + W holds
ex v1 being Element of V st
( v1 in W & v + v1 = u )

let V be non empty right_complementable vector-distributive scalar-distributive scalar-associative scalar-unital Abelian add-associative right_zeroed ModuleStr over GF; :: thesis: for u, v being Element of V
for W being Subspace of V st v + W = u + W holds
ex v1 being Element of V st
( v1 in W & v + v1 = u )

let u, v be Element of V; :: thesis: for W being Subspace of V st v + W = u + W holds
ex v1 being Element of V st
( v1 in W & v + v1 = u )

let W be Subspace of V; :: thesis: ( v + W = u + W implies ex v1 being Element of V st
( v1 in W & v + v1 = u ) )

assume v + W = u + W ; :: thesis: ex v1 being Element of V st
( v1 in W & v + v1 = u )

then v in u + W by Th44;
then consider u1 being Element of V such that
A1: v = u + u1 and
A2: u1 in W ;
take v1 = u - v; :: thesis: ( v1 in W & v + v1 = u )
0. V = (u + u1) - v by
.= u1 + (u - v) by RLVECT_1:def 3 ;
then v1 = - u1 by VECTSP_1:16;
hence v1 in W by ; :: thesis: v + v1 = u
thus v + v1 = (u + v) - v by RLVECT_1:def 3
.= u + (v - v) by RLVECT_1:def 3
.= u + (0. V) by VECTSP_1:19
.= u by RLVECT_1:4 ; :: thesis: verum