Sum of all the solution(s) of the equation <span class="math-inline">\log_{10}(x) + \log_{10}(x + 2) - \log_{10}(5x + 4) = 0</span> is -
<span class="math-inline">-1</span>
<span class="math-inline">3</span>
<span class="math-inline">4</span>
<span class="math-inline">5</span>