51. a) 0,5 + \(\frac{1}{3};\)

a) \(0,5 + \frac{1}{3} = \frac{1}{2} + \frac{1}{3} = \frac{1 \cdot 3}{2 \cdot 3} + \frac{1 \cdot 2}{3 \cdot 2} = \frac{3}{6} + \frac{2}{6} = \frac{3+2}{6} = \frac{5}{6}\)

Ответ: \(\frac{5}{6}\)