Jawabanmu

2014-05-13T19:02:18+07:00
1/si = 1/f - 1/so = 1/30 - 1/60 = 2/60 - 1/60 = 1/60
jadi si nya 60
1 5 1
2014-05-13T19:03:51+07:00
1/f = 1/so + 1/si
1/30 = 1/60 + 1/si
1/30-1/60 = 1/si
1/60 = 1/si
si = 60