20. Mark studied a group of 30 whales. If each whale weighed approximately \( 3.8 \times 10^{5} \) pounds, find the total weight of all 30 whales. Express your answer in scientific notation.

\( \frac{12}{13}+\frac{1}{13}+\frac{10}{13}=\square \) (Type an integer or a fraction.)

Perform the indicated operation and simplify the result. \( \frac{4}{15}+\frac{2}{15} \) \( \frac{4}{15}+\frac{2}{15}=\square \) (Type a simplified fraction.)

5. RESOLVA A OPERACAD : \( \frac{1}{3}+\frac{2}{5} \)

1. \( \begin{array}{r}37-(24-8) \\ (56-48): 8\end{array} \)

11. Arnaldo tinha 100 reais e gastou \( \frac{3}{7} \) do que tinha. Com quantos reais ficou Arnaldo? a) 40 b) 50 c) 60 d) 70 e) 80