Математика 5 класс учебник Никольский, Потапов ответы – номер 853

а) 31/80 + (3/16 + 39/80) = 3/16 + (31/80 + 39/80) = 3⁽⁵/16 + 70/80 = 15/80 + 70/80 = 85/80 = 17/16; б) 2/45 + (3/45 + 7/9) = (2/45 + 3/45) + 7/9 = 5/45 + 7⁽⁵/9 = 5/45 + 35/45 = 40/45 = 8/9; в) (3/7 + 5/14) + 1/14 = 1/7 + (5/14 + 1/14) = 3⁽²/7 + 6/14 = 6/14 + 6/14 = 12/14 = 6/7; г) 7/15 + (2/15 + 1/5) = 9/15 + 1⁽³/5 = 9/15 + 3/15 = 12/15 = 4/5; д) 3/16 + (1/16 + 5/8) = (3/16 + 1/16) + 5/8 = 4/16 + 5⁽²/8 = 4/16 + 10/16 = 14/16 = 7/8; е) (1/13 + 1/14) + 12/13 = (1/13 + 12/13) + 1/14 = 13/13 + 1/14 = 1 + 1/14 = 14/14 + 1/14 = 15/14.