To find out how many weeks it will take for Maria's account to reach $259, we can let \( x \) represent the number of weeks. She starts with $50 and saves $19 each week. Therefore, we can represent the total amount in her account after \( x \) weeks as:
\[ 19x + 50 = 259 \]
So, the correct equation in the form \( px + q = r \) is:
\[ 19x + 50 = 259 \]
This is the equation that represents the problem.