Answer
-12.3.
Work Step by Step
The distance between the two lenses equals the sum of the focal lengths.
$$f_1+f_2=1.20m$$
$$f_1=1.20m-0.0900m=1.11m$$
For a telescope, $M=-\frac{f_1}{f_2}$.
$$M=-\frac{f_1}{f_2}=-\frac{1.11m}{0.0900m}=-12.3$$