English
Let n, a, b, c, d be natural numbers. If c ≡ d (mod n) and a + c ≡ b + d (mod n), then a ≡ b (mod n).
Русский
Пусть n, a, b, c, d — натуральные числа. Если c ≡ d (mod n) и a + c ≡ b + d (mod n), то a ≡ b (mod n).
LaTeX
$$$ (c \equiv d \pmod{n}) \land (a+c \equiv b+d \pmod{n}) \Rightarrow a \equiv b \pmod{n} $$$
Lean4
protected theorem add_right_cancel (h₁ : c ≡ d [MOD n]) (h₂ : a + c ≡ b + d [MOD n]) : a ≡ b [MOD n] :=
by
rw [add_comm a, add_comm b] at h₂
exact h₁.add_left_cancel h₂