Answer
$5.52\times10^{-4}\ mol$
$346.26\ mg$
Work Step by Step
Molar mass: $21\times12.011+15\times1.008+208.980\times3+15.999\times12=1086.28\ g/mol$
Mass fraction of Bi: $208.980\times3/1086.28\times100\%=57.71\%$
In two tablets:
$600.\times10^{-3}\ g\div1086.28\ g/mol=5.52\times10^{-4}\ mol$
Mass of bismuth:
$600.\ mg\times57.71/100=346.26\ mg$
