exact (M.subset_cl _ hI.indep.subset_ground x_mem)
case intro.refine'_1.inr
α : Type u_1
M : Matroid α
I✝ B : Set α
Ys Xs : Set (Set α)
e : α
X : Set α
C : M.ModularCut
he : e ∉ M.E
hX : M.cl X ∉ C
heX : e ∉ X
I : Set α
hI : M.Basis' I X
ex_basis : (C.extension e).Basis' I X
x : α
x_mem✝ : x ∈ (C.extension e).cl I
x_mem : x ∈ I
⊢ x ∈ M.cl I
no goals