Jawabanmu

2014-08-14T18:18:36+07:00
A) 13a-8b+12a+9b = 13a+12a-8b+9b = 25a+b
b) 42n+35m+7-50m+20n-9 = 42n+20n+35m-50m+7-9 = 62n-15m-2