apply FreeCMonoid.eq
α : Type u
inst✝¹ : LinearLT α
inst✝ : DecidableRel LT.lt
x y : FreeCMonoid α
⊢ { vars := KVChain.mergeWith (fun x a b => some (valAdd a b)) x.vars y.vars } =
    { vars := KVChain.mergeWith (fun x a b => some (valAdd a b)) y.vars x.vars }
case a
α : Type u
inst✝¹ : LinearLT α
inst✝ : DecidableRel LT.lt
x y : FreeCMonoid α
⊢ { vars := KVChain.mergeWith (fun x a b => some (valAdd a b)) x.vars y.vars }.vars =
    { vars := KVChain.mergeWith (fun x a b => some (valAdd a b)) y.vars x.vars }.vars