exact Nat.eq_of_mul_eq_mul_right card_pos this
G : Type u_1
inst✝¹ : Group G
H K : Subgroup G
inst✝ : Fintype G
h' : card G = card ↥H * card ↥K
this : card (G ⧸ H) * card ↥H = card ↥K * card ↥H
⊢ card (G ⧸ H) = card ↥K
no goals