Ответ:

19.  1 3/4

20.  7 3/5

21.  3 1/4

22. 5

23.  1 3/10

24.  3 3/4

Пошаговое объяснение:

19. (3/4 - 1/6) * 3 = (9/12 - 2/12) * 3 = 7/12 * 3 = 7/4 = 1 3/4

20. (2/5 + 13/15)*6 = (6/15+13/15)*6 = 19/15*6 = 38/5 = 7 3/5

21. (3/8-1/20)*10 = (15/40-2/40)*10 = 13/40*10 = 13/4 = 3 1/4

22. (2/20+7/30)*15 = (6/60+14/60)*15 = 20/60*15 = 20/4 = 5

23. (9/10-7/15)*3 = (27/30-14/30)*3 = 13/30*3 = 13/10 = 1 3/10

24. (1/6+1/4)*9 = (2/12+3/12)*9 = 5/12*9 = 15/4 = 3 3/4