280:x=7 какой правильный ответ?

Question

Математика: 280:x=7 какой правильный ответ?

belozerovanastya · Accepted Answer

28/67 * (a - 2 11/13 : b) : c

при а = 10 11/13, b = 1/2, с = 3 1/2

28/67 * (10 11/13 - 2 11/13 : 1/2) : 3 1/2 = 8/13

1) 2 11/13 : 1/2 = 37/13 * 2 = 74/13 = 5 9/13

2) 10 11/13 - 5 9/13 = 5 2/13

3) 28/67 * 5 2/13 = 28/67 * 67/13 = 28/13

4) 28/13 : 3 1/2 = 28/13 : 7/2 = 28/13 * 2/7 = 8/13

(12 : а + b) : 1 1/2 - с

при а = 3 3/5, b = 2/3, с = 1 1/3

(12 : 3 3/5 + 2/3) : 1 1/2 - 1 1/3 = 1 1/3

1) 12 : 3 3/5 = 12 : 18/5 = 12 * 5/18 = 60/18 = 30/9 = 10/3

2) 10/3 + 2/3 = 12/3 = 4

3) 4 : 1 1/2 = 4 : 3/2 = 4 * 2/3 = 8/3

4) 8/3 - 1 1/3 = 8/3 - 4/3 = 4/3 = 1 1/3