Q. Two convex lenses of focal length 10 cm are placed 30 cm apart. An object is placed 20 cm to the left of lens 1. Calculate the position of the final image relative to the second lens:

A -25 cm
B +10 cm
C +25 cm
D at infinity
E -10 cm

Thank you

I know that I have to use the formula:
1/d0+1/di = 1/f and we are trying to find 1/di(1) first.

1/di(1) = 1/10 - 1/20 = di = 20cm

I'm not sure how to find di2

Now that you've found the first image, could you treat that as the object being "reflected" in the second lens? Use di1=do2 for this particular instance.
I'm assuming you know the focal length of the 2nd lens and can use the same equation as you did for the first part.