tolong jawab no 6,15,16,18

6)3-2/3+2×25=1/5×25=5th
15)[(13.00-06.30)-(2×15menit)]:8=(06.30-30menit):8=06.00:8=360menit:8=45menit
16)40m3=40.000.000cm:50.000cm=800detik
jam:detik=13600:800=3600:800=4,5
18)90/50=1.8jam w=1.8=01.48+40menit+07.15=09,43