а) 5,1 * 2/3 - 2 1/4 = 51/10 * 2/3 - 9/4 = 17/5 - 9/4 = 3,4 - 2,25 = 1,15

Ответ: 1,15

б) 1) 5 1/6 * 7,5 * 2,3 = 31/6 * 75/10 * 23/10 = 155/4 * 23/10 = 713/8 = 89 1/8 = 89,125

2) 4,6 * 2 7/12 * 4,5 = 46/10 * 31/12 * 45/10 = 713/60 * 45/10 = 2139/40 = 53 19/40 = 53,475

3) 89,125 : 53,475 = 89125/1000 : 53475/1000 = 89125/1000 * 1000/53475 = 89125/53475 = 5/3 = 1 2/3

Ответ: 1 2/3

в) 1 7/9 + (6,75 : 3,125 - 2,5 : 3,125) * 7,5 - 2 8/15 = 1 7/9 + ((6,75 - 2,5) : 3,125) * 7,5 - 2 8/15 = 1 7/9 + (4,25 : 3,125) * 7,5 - 2 8/15 = 1 7/9 + 1,36 * 7,5 - 2 8/15 = 1 7/9 + 10,2 - 2 8/15 = 1 7/9 + 10 2/10 - 2 8/15 = 1 70/90 + 10 18/90 - 2 48/90 = 9 4/9

Ответ: 9 4/9