Multiply both sides by the common denominator 16:

$\displaystyle{16}\cdot\frac{{{x}-{10}}}{{8}}=\frac{{x}}{{16}}\cdot{16}\usepackage{cmbright}\Huge\$

$\displaystyle\frac{{16}}{{8}}\cdot{\left({x}-{10}\right)}={x}\cdot\frac{{16}}{{16}}\usepackage{cmbright}\Huge\$

$\displaystyle{2}{\left({x}-{10}\right)}={x}\usepackage{cmbright}\Huge\$ or $\displaystyle{2}{x}-{20}={x}\usepackage{cmbright}\Huge\$

$\displaystyle{x}-{20}={0}\usepackage{cmbright}\Huge\$ , so $\displaystyle{x}={20}\usepackage{cmbright}\Huge\$