a b : Int
h✝ : b < a
h : b + -b < a + -b
⊢ 0 < a - b
a b : Int
h : b < a
⊢ 0 < a - b
have h := Int.add_lt_add_right h (-b)
no goals
a b : Int
h✝ : b < a
h : b + -b < a + -b
⊢ 0 < a - b
rwa [Int.add_right_neg] at h