Tolong jawab soal di atas dari nomor 15 sampai 25 dengan cara

15. A
16. 3/7 + 1/3
= 9/21 + 7/21
=16/21
17. 2/3 - 1/2
=4/6 - 3/6
= 1/6
18. 3/5 × 1/2
= 3/10
=0,3
19. 6 : 2/3
=6/1 : 2/3
=6/1 × 3/2
=18/2
=9
20. 9/12 : 1/2
=9/12 × 2/1
=18/12
=3/2
21. 3,18 × 1,15
=3,6570