Resposta:

a) 2/3 + 1/8

m.m.c(3, 8) = 24

2/3 = 16/24

1/8 = 3/24

16/24 + 3/24 = 19/24

Portanto, 2/3 + 1/8 = 19/24

b) 8/7 + 5/5

m.m.c(7, 5) = 35

8/7 = 40/35

5/5 = 7/35

40/35 + 7/35 = 47/35

Simplificando por 5, temos:

47/35 = 9/7

Portanto, 8/7 + 5/5 = 9/7

c) 5/4 - 10/9

m.m.c(4, 9) = 36

5/4 = 45/36

10/9 = 40/36

45/36 - 40/36 = 5/36

Portanto, 5/4 - 10/9 = 5/36

d) 7/12 + 14/5

m.m.c(12, 5) = 60

7/12 = 35/60

14/5 = 168/60

35/60 + 168/60 = 203/60

Simplificando por 4, temos:

203/60 = 50,75/15

Portanto, 7/12 + 14/5 = 50,75/15

e) 9/35 . 10/3

9/35 . 10/3 = 90/105 . 35/3

Simplificando 90/105, temos:

90/105 = 6/7

6/7 . 35/3 = 30/7

Portanto, 9/35 . 10/3 = 30/7

f) 69/70 . 3/2

69/70 . 3/2 = 207/140

Simplificando por 7, temos:

207/140 = 3/2

Portanto, 69/70 . 3/2 = 3/2

g) 6/8 ÷ 35/21

6/8 ÷ 35/21 = 6/8 x 21/35

Simplificando por 7, temos:

21/35 = 3/5

6/8 x 3/5 = 9/20

Portanto, 6/8 ÷ 35/21 = 9/20

h) 35/9 ÷ 12/3

35/9 ÷ 12/3 = 35/9 x 3/12

Simplificando por 3, temos:

3/12 = 1/4

35/9 x 1/4 = 35/36

Portanto, 35/9 ÷ 12/3 = 35/36