Ответ:

  1. \(\frac{6}{49}+\frac27=\frac{6}{49}+\frac{14}{49}=\frac{20}{49}\);
  2. \(\frac7{11}-\frac12=\frac{14}{22}-\frac{11}{22}=\frac3{22}\);
  3. \(\frac6{35}-\frac3{14}=\frac{12}{70}-\frac{15}{70}=-\frac3{70}\);
  4. \(\frac45-0,6=\frac45-\frac35=\frac15\).

Ответ: а) \(\frac{20}{49}\); б) \(\frac3{22}\); в) \(-\frac3{70}\); г) \(\frac15\).