| ∃ y, z. x = y + (a + z) ⊦ ∃ a0, x0, y, z. a ' + x = x0 + a0 ' + y + a0 ' + z |
⊦ ∃ a0, x, y0, z0. a ' + y + a ' + z = x + a0 ' + y0 + a0 ' + z0
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list%c: ⊦ a + x = a ' + x; from specification list