Answer
236 amu
Work Step by Step
Gallium sulfide has molecular formula =$Ga_2S_3$
So, the molecular weight of Gallium and Sulfur is:
Ga = 70 amu
S = 32 amu
MM ($Ga_2S_3$) = $(2\times70)+(3\times32) = 236 amu$
Note: 236 amu or 236 u, the two nomeclatures are equivalent.