To calculate the total score for 24 correct answers and 11 incorrect answers using the expression \( 15c - 10a \), we can substitute \( c = 24 \) and \( a = 11 \) into the expression.
\[ \text{Total Score} = 15c - 10a \] \[ = 15(24) - 10(11) \] \[ = 360 - 110 \] \[ = 250 \]
Therefore, the total score for 24 correct and 11 incorrect answers is 250 points.