1) 2 4/5 + 2 2/3 = 14/5 + 8/3 = (14 × 3 + 8 × 5)/15 = 42/15 + 40/15 = 82/15 = 5 7/15
2) 10 13/30 - 3,6 = 10 13/30 - 3 6/10 = 313/30 - 36/10 =313/30 - 18/5 =(313 × 1 - 18 × 6)/30 = 313/30 - 108/30 = 205/30 = 41/6 = 6 5/6
3) 5 7/15 ÷ 6 5/6 = 82/15 ÷ 41/6 = 82/15 × 6/41 = 4/5 = 0,8
4) 0,8 * 1,25 = 1
ОТВЕТ : 1