Answer
$\frac{f_1}{f_2}$
Work Step by Step
We know that for the first lens
$tan\theta=\frac{d_1}{2f_1}$.....eq(1)
and for the second lens
$tan\theta=\frac{d_2}{2f_2}$.....eq(2)
Now, comparing eq(1) and eq(2), we obtain:
$\frac{d_1}{2f_1}=\frac{2f_1}{2f_2}$
This can be rearranged as:
$\frac{d_1}{d_2}=\frac{2f_1}{2f_2}$
$\frac{d_1}{d_2}=\frac{f_1}{f_2}$
