To solve the problem, let \( x \) represent the number of weekdays Lindsay practiced.
We know:
- She practices 50 minutes on Saturday.
- She practices 30 minutes on each weekday.
- Last week, she practiced a total of 140 minutes.
We can set up the equation based on her total practice time. The total time she practiced can be expressed as the sum of her Saturday practice and her weekday practice:
\[ 50 + 30x = 140 \]
Here, 50 represents the minutes practiced on Saturday, and \( 30x \) represents the minutes practiced on \( x \) weekdays.
Thus, the equation in the form \( px + q = r \) is:
\[ 30x + 50 = 140 \]
Where:
- \( p = 30 \)
- \( q = 50 \)
- \( r = 140 \)