Ответ:

  1. \(5\frac{1}{4}=\frac{5\cdot4+1}{4}=\frac{21}{4}\).
  2. \(2\frac{12}{50}=\frac{2\cdot50+12}{50}=\frac{112}{50}=\frac{56}{25}\).
  3. \(12\frac{2}{3}=\frac{12\cdot3+2}{3}=\frac{38}{3}\).
  4. \(4\frac{3}{7}=\frac{4\cdot7+3}{7}=\frac{31}{7}\).

Ответ: а) \(\frac{21}{4}\); б) \(\frac{56}{25}\); в) \(\frac{38}{3}\); г) \(\frac{31}{7}\).