True statements: a) x + y = y + x ⇒ commutative property of addition b) (x * y) * z = x * (y * z) ⇒ associative property of multiplication d) (x + y) + z = x + (y + z) ⇒ associative property of addition
False statements: c) x - y = y - x should be: x - y = - y + x e) (x - y) - z = x - (y - z) should be: (x - y) - z = x - (y + z)