assign(max_seconds, 30). formulas(sos). (x * e) * x = x. x * (x * y) = y. (x * y) * (z * u) = (x * z) * (y * u). ((x * x) * x) * x = e. end_of_list. formulas(goals). x * y = x * z -> y = z. end_of_list.