Answer
Please see the work below.
Work Step by Step
We know that
$0.2122g \space TH\times \frac{1mol\space TH}{331.28g\space TH}\times \frac{504.83g\space TI_2SO_4}{1mol\space TI_2SO_4}=0.16168g\space TI_2SO_4$
Thus $Ti_2SO_4=\frac{0.16168}{0.7590}\times 100\%=21.30\%$