1.

1)

[tex] \frac{6}{x} = \frac{36}{30} \\ x = \frac{6 \times 30}{36} \\ x = \frac{1 \times 5}{1} \\ x = 5[/tex]

2)

[tex] \frac{12}{7} = \frac{3}{x} \\ x = \frac{3 \times 7}{12} \\ x = \frac{7}{4} \\ x = 1 \frac{3}{4} \\ x = 1.75[/tex]

3)

[tex] \frac{4.9}{0.35} = \frac{x}{35} \\ x = \frac{4.9 \times 35}{0.35} \\ x = \frac{49 \times 35 \times 10}{35} \\ x = 490[/tex]

4)

[tex] \frac{16}{12} = \frac{68}{51} = \frac{4}{3} [/tex]

5)

[tex] \frac{x}{9} = \frac{2}{23} \\ x = \frac{9 \times 2}{23} \\ x = \frac{18}{23} [/tex]

2.

[tex](3 \frac{1}{3} + 2.5)(4.6 - 2 \frac{1}{3} ) = (3 \frac{1}{3} + 2 \frac{1}{2} )(4 \frac{3}{5} - 2 \frac{1}{3} ) = \\ = (3 \frac{2}{6} + 2 \frac{3}{6} )(4 \frac{9}{15} - 2 \frac{5}{15} ) = 5 \frac{5}{6} \times 2 \frac{4}{15} = \\ = \frac{35 \times 34}{6 \times 15} = \frac{7 \times 17}{3 \times 3} = \frac{119}{9} = 13 \frac{2}{9} [/tex]