6.58 Найдите сумму: a) 8/13 + 3/13; б) 31/60 + 29/60 в) 18 + 4/19; г) 23 + 9/10; д) 2 7/9 + 8/9; е) 15 8/11 + 4 3/11; ж) 4 1/2 + 3 1/4; з) 5 1/7 + 3 20/21.

a) 8/13 + 3/13 = (8+3)/13 = 11/13

б) 31/60 + 29/60 = (31+29)/60 = 60/60 = 1

в) 18 + 4/19 = 18 4/19

г) 23 + 9/10 = 23 9/10

д) 2 7/9 + 8/9 = 2 + (7+8)/9 = 2 + 15/9 = 2 + 1 6/9 = 3 6/9 = 3 2/3

е) 15 8/11 + 4 3/11 = (15 + 4) + (8/11 + 3/11) = 19 + 11/11 = 19 + 1 = 20

ж) 4 1/2 + 3 1/4 = 4 + 1/2 + 3 + 1/4 = (4 + 3) + (1/2 + 1/4) = 7 + (2/4 + 1/4) = 7 + 3/4 = 7 3/4

з) 5 1/7 + 3 20/21 = 5 + 1/7 + 3 + 20/21 = (5+3) + (1/7 + 20/21) = 8 + (3/21 + 20/21) = 8 + 23/21 = 8 + 1 2/21 = 9 2/21

Ответ: a) 11/13; б) 1; в) 18 4/19; г) 23 9/10; д) 3 2/3; е) 20; ж) 7 3/4; з) 9 2/21