Verified answer

№ 510

1) (7/15 - 1/6) + 2/5 = (14/30 - 5/30) + 2/5 = 9/30 + 2/5 = 3/10 + 2/5 = 3/10 + 4/10 = 7/10 = 0,7

2) (3/8 - 1/9) + 25/36 = (27/72 - 8/72) + 25/36 = 19/72 + 25/36 = 19/72 + 50/72 = 69/72 = 23/24

3) (8/9 - 5/6) + 2/3 = (16/18 - 15/18) + 2/3 = 1/18 + 2/3 = 1/18 + 12/18 = 13/18

4) (7/8 - 13/20) + 9/10 = (35/40 - 26/40) + 9/10 = 9/40 + 9/10 = 9/40 + 36/40 = 45/40 = 9/8 = 1 1/8

5) (7/18 - 1/12) + 5/6 = (14/36 - 3/36) + 5/6 = 11/36 + 5/6 = 11/36 + 30/36 = 41/36 = 1 5/36

6) (3/4 - 8/15) + 17/20 = (45/60 - 32/60) + 17/20 = 13/60 + 17/20 = 13/50 + 51/60 = 64/60 = 1 4/60 = 1 1/15

№ 511

                    5 + 3

1) 1/3 + 1/5 = ------------ = 8/15

                       15

                      9 + 5

2) 1/5 + 1/9 = ------------ = 14/45

                        45

                     4 + 7

3) 1/7 + 1/4 = --------- = 11/28

                       28

                      8 + 3

4) 1/3 + 1/8 = -----------= 11/24

                       24

                       2 + 3

5) 1/3 + 1/2 = ----------- = 5/6

                          6

                     7 + 6

6) 1/6 + 1/7 = ---------- = 13/42

                       42