Jawabanmu

2014-01-23T18:28:27+07:00
V=s/t
s= vt
s=20.45menit = 20.3/4jam =15km

v=s/t 
v= 15/30menit = 15/1/2jam = 15.2 =30 km/jam
2014-01-23T18:32:40+07:00
3/4 = x
1/2    20
1/2x = 3/4.20
1/2x = 3.5
1/2x = 15
x = 15
     1/2
x = 15.2 = 30