2012 Fermat Problem 9

Mary and Sally were once the same height. Since then, Sally grew 20\% taller and Mary's height increased by half as many centimetres as Sally's height increased. Sally is now 180 cm tall. How tall, in cm, is Mary now?

\textbf{(A)}\ 144\quad \textbf{(B)}\ 165\quad \textbf{(C)}\ 162\quad \textbf{(D)}\ 150\quad \textbf{(E)}\ 170

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Fermat contests here.