Answer
The solution set is $\left ( -\frac{5}{3},-1 \right )$.
Work Step by Step
The given inequality is
$3x^2+8x+5<0$
Factor the left hand side.
$3x^2+5x+3x+5<0$
$x(3x+5)+1(3x+5)<0$
$(3x+5)(x+1)<0$
Both factors are less than zero.
$(3x+5)