Theorem: Matroid.delete_r_eq' (Matroid/Minor/Rank.lean)

State before:
α : Type u_1
M✝ N : Matroid α
I J C D✝ X✝ Y Z : Set α
e f : α
M : Matroid α
D X : Set α
⊢ (M ＼ D).r X = M.r (X \ D)
Tactic:
rw [r, r, delete_er_eq']
State after:
no goals