[tex]a) \: x \times \frac{3}{5} = 12 \\ \\ \frac{3x}{5} = 12 \\ \\ 3x = 60 \\ \\ x = \frac{60}{3} \\ \\ x = 20[/tex]

[tex]b) \: x \div \frac{1}{6} = 30 \\ \\ 6x = 30 \\ \\ x = \frac{30}{6} \\ \\ x = 5[/tex]

[tex]c) \: x \times 1 \frac{1}{4} = 15 \\ \\ x \times \frac{5}{4} = 15 \\ \\ \frac{5x}{4} = 15 \\ \\ 5x = 60 \\ \\ x = \frac{60}{5} \\ \\ x = 12[/tex]

[tex]d) \: x \div 2 \frac{2}{3} = 9 \\ \\ x \div \frac{8}{3} = 9 \\ \\ \frac{3x}{8} = 9 \\ \\ 3x = 72 \\ \\ x = \frac{72}{3} \\ \\ x = 24[/tex]