#check ∃ x > 10, x = 15
#check ∃ x < 10, x = 5
#check ∃ x ≥ 10, x = 15
#check ∃ x ≤ 10, x = 5
#check ∀ x > 10, x ≠ 5
#check ∀ x < 10, x ≠ 15
#check ∀ x ≥ 10, x ≠ 5
#check ∀ x ≤ 10, x ≠ 15