4 Вычислите: б) \(\frac{7}{9}\) + \(\frac{1}{15}\) - \(\frac{5}{18}\) + \(\frac{1}{30}\).

б) \(\frac{7}{9}\) + \(\frac{1}{15}\) - \(\frac{5}{18}\) + \(\frac{1}{30}\)

Приведем дроби к общему знаменателю 90:

\(\frac{7}{9} = \frac{7 \cdot 10}{9 \cdot 10} = \frac{70}{90}\)

\(\frac{1}{15} = \frac{1 \cdot 6}{15 \cdot 6} = \frac{6}{90}\)

\(\frac{5}{18} = \frac{5 \cdot 5}{18 \cdot 5} = \frac{25}{90}\)

\(\frac{1}{30} = \frac{1 \cdot 3}{30 \cdot 3} = \frac{3}{90}\)

Тогда:

\(\frac{7}{9} + \frac{1}{15} - \frac{5}{18} + \frac{1}{30} = \frac{70}{90} + \frac{6}{90} - \frac{25}{90} + \frac{3}{90} = \frac{70+6-25+3}{90} = \frac{54}{90} = \frac{3}{5}\)

Ответ: \(\frac{3}{5}\)