To find out how many votes Mary received, you can calculate 75% of the total votes cast, which is 1200.
Here's the calculation:
\[ \text{Votes for Mary} = 75% \text{ of } 1200 = 0.75 \times 1200 \]
Now, perform the multiplication:
\[ 0.75 \times 1200 = 900 \]
Therefore, Mary received 900 votes.