84=2×2×3×7
90=2×3×3×5
312=2×2×2×3×13
392=2×2×2×7×7
2500=2×2×5×5×5×5
1600=2×2×2×2×2×2×5×5
1) (5/21 + 2/15) + 2/21 = 5/21 + 2/21 + 2/15 = 7/21 + 2/15 = 1/3 + 2/15 = 5/15 + 2/15 = 7/15
(2/35 + 3/28) + 1/28 = 3/28 + 1/28 + 2/35 = 4/28 + 2/35 = 1/7 + 2/35 = 5/35 + 2/35 = 7/35 = 1/5
Извини 2 не знаю
Что? как может сумма двузначных чисел быть 10?
17/34= 3/6
3= 18/6
4/9= 8/18
65/78= 15/18
1.5= 1 1/2= 3/2= 27/18
2/3= 12/18
46/72= 23/36
1= 36/36
25/45= 20/36
11/18= 22/36