tolong dibantu dan pakai cara..

3.selisih=waktu dika-waktu ana
=12menit 32 detik-8menit 28 detik
=4menit 4detik
5.=7.15+2jam=9.15
6.=11.30+2.00.35=13.30.35
7.=17.25-16.30-(5×2)
=17.25-16.30-10
=45 menit
8.=2,5km×20menit=50km/menit
=50km/menit........m/menit
=50km×1000m=50.000m
=50.000m/menit