Theorem: Tutorial.inv_mul_cancel_right (Solution/Advanced/Algebra/Lecture1.lean)

State before:
A : Type ?u.13426
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ a * b⁻¹ * b = a
Tactic:
simp [mul_assoc]
State after:
no goals