а)

25 * (\frac{7}{10} + \frac{3}{5} + \frac{1}{2})

;
б)

5 : 1 \frac{1}{4} + 7 : 1 \frac{1}{3}

а) 25 ∗ ( 7 10 + 3 5 + 1 2 ) ; б) 5 : 1 1 4 + 7 : 1 1 3 .

25 * (\frac{7}{10} + \frac{3}{5} + \frac{1}{2}) = 25 * \frac{7 + 3 * 2 + 1 * 5}{10} = 25 * \frac{7 + 6 + 5}{10} = 25 * \frac{18}{10} = 25 * \frac{9}{5} = 5 * 9 = 45

5 : 1 \frac{1}{4} + 7 : 1 \frac{1}{3} = 5 : \frac{5}{4} + 7 : \frac{4}{3} = 5 * \frac{4}{5} + 7 * \frac{3}{4} = 1 * \frac{4}{1} + \frac{21}{4} = 4 + 5 \frac{1}{4} = 9 \frac{1}{4}