[tex]\displaystyle\bf\\1)\\\\\frac{5}{18}=\frac{x}{3} \\\\\\x=\frac{5\cdot 3}{18} =\frac{5}{6} \\\\\\2)\\\\\frac{7}{4} =\frac{3}{5x} \\\\\\5x=\frac{3\cdot 4}{7} \\\\\\5x=\frac{12}{7} \\\\\\x=\frac{12}{7} :5=\frac{12}{7} \cdot \frac{1}{5} =\frac{12}{35} \\\\\\x=\frac{12}{35} \\\\\\3)\\\\\frac{3}{7} =\frac{x+2}{5} \\\\\\x+2=\frac{3\cdot 5}{7} \\\\\\x+2=\frac{15}{7} \\\\\\x+2=2\frac{1}{7} \\\\\\x=2\frac{1}{7} -2=\frac{1}{7}[/tex]

[tex]\displaystyle\bf\\x=\frac{1}{7}[/tex]