请教大牛TTGWD30 Q11, Q13！！！

Q11:

If a and b are integers, is b even?

(1)
                    3a + 4b is even.

(2)             3a + 5b is even.

If a and b are integers, is b even?

(1)
        3a + 4b is even.

(2)             3a + 5b is even.

Q13:

If x + y is an integer, is y an integer?

(1)
              x – y is an integer.

(2)
              x + 2y is an integer.

Q11 C even-even＝even

Q13 B (X+2Y)-(X+Y)=Y integer-integer=integer

right?

重谢！！！