This one is the Law of Sines again.
The Law of Sines relies on the standard labeling of triangle ABC with vertices A, B, and C and respective opposite sides of a, b and c. Then
[tex]\dfrac{a}{\sin A} = \dfrac{b}{\sin B} = \dfrac{c}{\sin C}[/tex]
Here we have A=150 degrees (opposite side a), b= 10 cm and B = 12 degrees. We seek a.
So we need the first equation of the Law of Sines:
[tex]\dfrac{a}{\sin A} = \dfrac{b}{\sin B}[/tex]
[tex]a = \dfrac{b \sin A }{\sin B}[/tex]
[tex]a = \dfrac{10 \sin 150}{\sin 12} \approx 28.0[/tex]
