$E_B=\frac{m_e{c}^2}{\sqrt{1-\frac{v^2}{c^2}}}$

$\frac{E_B}{E_0}=\frac{\frac{m_e{c}^2}{\sqrt{1-\frac{v^2}{c^2}}}}{E_0}$

$E_0=m_e{c}^2$

$\frac{E_B}{E_0}=\frac{\frac{m_e{c}^2}{\sqrt{1-\frac{v^2}{c^2}}}}{m_e{c}^2}$

$\frac{E_B}{E_0}=\frac{\cancel{m_e{c}^2}}{\sqrt{1-\frac{v^2}{c^2}}}\cdot \frac{1}{\cancel{m_e{c}^2}}$

$\frac{E_B}{E_0}=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$

$\frac{E_B}{E_0}=\frac{1}{\sqrt{1-\frac{{\left(2,00\cdot 10^8\frac{\mathrm{m}}{\mathrm{s}}\right)}^2}{{\left(3,00\cdot 10^8\frac{\mathrm{m}}{\mathrm{s}}\right)}^2}}}=\frac{1}{\sqrt{1-\frac{4\cdot \cancel{10^{16}}\cancel{\frac{{\mathrm{m}}^2}{{\mathrm{s}}^2}}}{9\cdot \cancel{10^{16}}\cancel{\frac{{\mathrm{m}}^2}{{\mathrm{s}}^2}}}}}=$

$=\frac{1}{\sqrt{\frac{9}{9}-\frac{4}{9}}}=\frac{1}{\sqrt{\frac{5}{9}}}=\frac{1}{\frac{\sqrt{5}}{3}}=\frac{3}{\sqrt{5}}\approx \frac{3}{2,236}\approx 1,34$