rw [Multiset.count_sub]
case a
α : Type u_1
inst✝ : Preorder α
dec : DecidableEq α
M N P Q : Multiset α
h : M + N = P + Q
x : α
⊢ Multiset.count x N = min (Multiset.count x N) (Multiset.count x Q) + Multiset.count x (P - M)
case a
α : Type u_1
inst✝ : Preorder α
dec : DecidableEq α
M N P Q : Multiset α
h : M + N = P + Q
x : α
⊢ Multiset.count x N = min (Multiset.count x N) (Multiset.count x Q) + (Multiset.count x P - Multiset.count x M)