Ответ:

2/9+3/8=16+27/72=43/72 ;

2/3-1/4=8-3/12=5/12;

75/88-31/40=375-341/440=34/440=17/220;

27/30+21/24=9/10+7/8=36+35/40=71/40:

27/32-21/40=135-84/160=51/160;

29/30+47/48-15/16=232+235-225/240=242/240=121/120.

Пошаговое объяснение:

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Відповідь:

2/9+3/8 = (2*8+3*9)/72 = (16+27)/72 = 43/72

2/3-1/4 = (2*4-1*3)/12 = (8-3)/12 = 5/12

75/88-31/40 = (75*5 - 31*11)/440 = (375-341)/440 = 34/440 = 17/220

27/30+21/24 = (27*4+21*5)/120 = (108+105)/120 = 213/120 = 1  93/120

27/32-21/40 = (27*5 - 21*4)/160 = (135-84)/160 = 51/160

29/30+47/48-15/16 = (29*8+47*5 - 15*15)/240 = (232+235-225)/240 = 242/240 = 1  2/240 = 1  1/120