tolong yang jago matematika noner 9dan 11 dengan caranya yang lengkap banget

9)
4x + 20
-----------
3x + 15

....4(x + 5)
= ------------
....3(x + 5)

= 4/3
= 1 1/3

11)
a - 5
-------
5 - a

...a - 5.......-1
= ------- × ------
....5 - a......-1

...-(a - 5)
= ----------
.. -(5 - a)

.....-a + 5
= ----------
....-(5 - a)

......5 - a
= -----------
....-(5 - a)

= 1/-1
= -1