Jawabanmu

2014-06-03T13:35:05+07:00
1/s' = 1/s - 1/f
1/s' = 1/25 - 1/12
1/s' = 23
2014-06-03T15:02:59+07:00
25 . 12 per 25 + 12 = 300 / 37 = 8,1