Answer
$0.375I_0 $.
Work Step by Step
The first polarizer filters out half the incident light.
$$I_1=\frac{1}{2}I_o$$
The fraction filtered out by the second polarizer depends on the angle between the axes of the two filters, which is 30 degrees.
$$I_2=I_1cos^2\theta=\frac{1}{2}I_o cos^230^{\circ}=0.375I_0 $$
