Solution:
From the properties of a Rhombus;
Opposite angles of a rhombus are equal.
The adjacent angles of a rhombus are supplementary, i.e. adds up to 180°
If one of the angles of a rhombus 120°, and the sum of the adjacent angles is 180°, then, the adjacent angle will be 60° (180° - 120° = 60°)
If one of the angles of a rhombus is 30°, then, the adjacent angle will be 150° (180° - 30° = 150°)
Thus, the sum of 120° and 30° is not supplementary and definitely can not be adjacent, since they do not sum up to 180°.
Hence, it is not possible