Ответ:

  1. а) \(\frac13+\frac56=\frac26+\frac56=\frac76=1\frac16\); б) \(\frac57-\frac1{14}=\frac{10}{14}-\frac1{14}=\frac9{14}\); в) \(2\frac23+5\frac5{12}=2\frac8{12}+5\frac5{12}=8\frac1{12}\).
  2. а) \(\frac3{11}-\frac1{13}=\frac{39-11}{143}=\frac{28}{143}\); б) \(\frac7{20}+\frac23=\frac{21+40}{60}=\frac{61}{60}=1\frac1{60}\); в) \(3\frac2{15}-1\frac17=\frac{47}{15}-\frac87=\frac{329-120}{105}=\frac{209}{105}=1\frac{104}{105}\).
  3. а) \(\frac5{34}-\frac{41}{51}=\frac{15-82}{102}=-\frac{67}{102}\); б) \(1\frac1{30}-5\frac7{90}=\frac{94}{90}-\frac{457}{90}=-\frac{363}{90}=-4\frac1{30}\); в) \(6\frac17-10\frac3{14}=\frac{85}{14}-\frac{143}{14}=-\frac{58}{14}=-4\frac17\).