А)7 4/9-3 2/9+4 5/9 б)4 7/15+8 8/15-6 14/15 в)(4 21/23+6 8/23)- 3 21/23

А) 7 4/9 - 3 2/9 + 4 5/9 = (7 * 9 + 4)/9 - (3 * 9 + 2)/9 + (4 * 9 + 5)/9 = (63 + 4)/9 - (27 + 2)/9 + (36 + 5)/9 = 67/9 - 29/9 + 41/9 = (67 - 29 + 41)/9 = 79/9;

б) 4 7/15 + 8 8/15 - 6 14/15 = (4 * 15 + 7)/15 + (8 * 15 + 8)/15 - (6 * 15 + 14)/15 = (60 + 7)/15 + (120 + 8)/15 - (90 + 14)/15 = 67/15 + 128/15 - 104/15 = (67 + 128 - 104)/15 = 91/15;

в) (4 21/23 + 6 8/23) - 3 21/23 = (4 * 23 + 21)/23 + (6 * 23 + 8)/23 - (3 * 23 + 21)/23 = (92 + 21)/23 + (138 + 8)/23 - (69 + 21)/23 = (113 + 146 - 90)/23 = 169/23.