Пошаговое объяснение:
а) 5/9 - 2/5 = 5*5/9*5 - 2*9/5*9 = 25/45 - 18/45 = 7/45
б) 65/28 : 5/4 = 65/28 * 4/5 = 65*4/28*5 = 13/7 = 1 6/7
3.
1) 40/72 = 5/9
2) 5/9 - 1/3 = 5/9 - 3/9 = 2/9
3) 2/9 * 2 1/4 = 2/9 * 9/4 = 1/2
4) 1/2 + 8/9 = 9/18 + 16/18 = 25/18 = 1 7/18
