Resposta:

[tex]a)3x - 4 = 20 \\ 3x = 20 + 4 \\ 3x = 24 \\ x = \frac{24}{3} \\ x = 8[/tex]

[tex]b)7x + 2 = 37 \\ 7x = 37 - 2 \\ 7x = 35 \\ x = \frac{35}{7} \\ x = 5[/tex]

[tex]c) \frac{2}{x} + 5 = 7 \\ \frac{2 + 5x}{x} = 7 \\ 2 + 5x = 7x \\ 2 = 7x - 5x \\ 2x = 2 \\ x = \frac{2}{2} \\ x = 1[/tex]

[tex]d) {3}^{7} \div {3}^{3} = \\ {3}^{7 - 3} = \\ {3}^{4} = 81[/tex]

[tex]e) \frac{2}{5} \times \frac{3}{4} = \\ \frac{2 \times 3}{5 \times 4} = \\ \frac{6}{20 } ( \div 2 \\ = \frac{3}{10} [/tex]

[tex] f){4}^{2} \times {4 }^{2} = \\ {4}^{2 + 2} = \\ {4}^{4} = 256[/tex]

[tex]g) \frac{3}{4} \div 2 = \\ \frac{3}{4} \div \frac{2}{1} = \\ \frac{3}{4} \times \frac{1}{2} = \\ \frac{3 \times 1}{4 \times 2} = \\ = \frac{3}{8} [/tex]