Решение:
\[ \frac{4}{9} + \frac{4}{18} = \frac{4 \times 2}{9 \times 2} + \frac{4}{18} = \frac{8}{18} + \frac{4}{18} \]
\[ \frac{8}{18} + \frac{4}{18} = \frac{8 + 4}{18} = \frac{12}{18} \]
\[ \frac{12}{18} = \frac{12 \div 6}{18 \div 6} = \frac{2}{3} \]
Ответ: $$\frac{2}{3}$$