Пошаговое объяснение:

№7

9/12 - 8/12 = (9-8)/12 = 1/12

7/10 - 3/10 = (7-3)/10 = 4/10 = 2/5

6/8 + 1/8 = (6+1)/8 = 7/8

5/6 + 1/6 = (5+1)/6 = 6/6 = 1

[tex] \frac{9}{12} - \frac{8}{12} = \frac{9 - 8}{12} = \frac{1}{12} [/tex]

[tex] \frac{7}{10} - \frac{3}{10} = \frac{7 - 3}{10} = \frac{4}{10} = \frac{2}{5} [/tex]

[tex] \frac{6}{8} + \frac{1}{8} = \frac{6 + 1}{8} = \frac{7}{8} [/tex]

[tex] \frac{5}{6} + \frac{1}{6} = \frac{5 + 1}{6} = \frac{6}{6} = 1[/tex]