Jawabanmu

2014-09-03T17:03:42+07:00
(13a - 8b)+(12a + 9b)
= 13a - 8b + 12a + 9b
= 13a +12a - 8b + 9b
= 25a + b
2014-09-03T17:04:56+07:00
(13a-8b)+(12a+9b)
=13a-8b+12a+9b
=25a+b