Jawabanmu

2014-04-23T21:51:02+07:00
1/10-1/20=1/so
4/40-2/40=1/so
2/40=1/so
20=so

2014-04-23T21:54:21+07:00
So= Si x f : (Si-F)
= 20 x 10 : ( 20-10) 
= 200 : 10 = 20