Voltage in RC circuit with unknown frequency
First of all you don't care about the frequency of the source, since you have the reactance of the caps:

\$X_C=-j\frac{1}{ωC} = -j \cdot\texttt{fixed}\$

\$R_2\$ and \$C_2\$ are in parallel, so:

\$R_2//X_{C_2} = \frac{R_2\cdot X_{C_2}}{R_2+ X_{C_2}}=\frac{333\cdot (-j250)}{333-j250}=\frac{83250\angle{-90}}{416.4\angle{-35.9}}=200\angle{-53.1}\$

Then, \$R_1, C_1\$ and \$R_2//X_{C_2}\$ are in series. Calculating the total Z can give you the current exiting the source and finally \$V_{R_1}=R1\cdot I\$.

Keep in mind that books make mistakes too...