Let \( x \) represent the number of weekdays Lindsey practiced. Since she practices 30 minutes each weekday, the total practice time on weekdays would be \( 30x \) minutes.
We know she practices for 50 minutes on Saturday. Therefore, the total practice time for the week can be expressed as:
\[ 30x + 50 = 140 \]
To fit the requested form \( px + q = r \), we can rearrange this as follows:
\[ 30x + 50 = 140 \]
So, the equation is:
\[ 30x + 50 = 140 \]
In this case, \( p = 30 \), \( q = 50 \), and \( r = 140 \).