I assume your equation is
1/s + 1/(s+3) + 1/(s+10) = 0
There are a couple different ways:
% With the Symbolic Math Toolbox
syms s
solve(1/s + 1/(s+3) + 1/(s+10))
% Numerically in base MATLAB. (Required multiplying through by the
% denominator terms, to get the coefficients.)
roots([3 26 30])