Ответ:

  1. \(\frac{a}{6}+\frac{b}{6}=\frac{a+b}{6}\).
  2. \(\frac{p}{3}-\frac{q}{3}=\frac{p-q}{3}\).
  3. \(\frac{x}{y}+\frac{3x}{y}=\frac{4x}{y}\).
  4. \(\frac{5m}{n}-\frac{3m}{n}=\frac{2m}{n}\).
  5. \[\frac{x+4y}{12}+\frac{2x+5y}{12}=\frac{x+4y+2x+5y}{12}=\frac{3x+9y}{12}=\frac{x+3y}{4}.\]
  6. \[\frac{a+2b}{2c}-\frac{a-4b}{2c}=\frac{a+2b-a+4b}{2c}=\frac{6b}{2c}=\frac{3b}{c}.\]
  7. \[\frac{4c+3d}{cd}-\frac{3d-2c}{cd}=\frac{4c+3d-3d+2c}{cd}=\frac{6c}{cd}=\frac{6}{d}.\]

Ответ: а) \(\frac{a+b}{6}\); б) \(\frac{p-q}{3}\); в) \(\frac{4x}{y}\); г) \(\frac{2m}{n}\); д) \(\frac{x+3y}{4}\); е) \(\frac{3b}{c}\); ж) \(\frac{6}{d}\).