To represent the problem with an equation in the form \( px + q = r \):
Maria starts with $50 and saves $19 each week. If \( x \) represents the number of weeks, the total amount in her account after \( x \) weeks can be expressed as:
\[ 19x + 50 = 259 \]
Therefore, the correct representation of the problem is:
19x + 50 = 259
This corresponds to the response:
19 x plus 50 equals 259.