To find the empirical probability of David's incorrect responses, we first need to determine how many questions he answered incorrectly.
He answered 70 questions in total and got 45 correct. Therefore, the number of incorrect responses is:
\[ 70 - 45 = 25 \]
Next, we calculate the empirical probability of getting an answer incorrect. This probability is given by the ratio of the number of incorrect responses to the total number of responses:
\[ P(\text{incorrect}) = \frac{\text{Number of incorrect responses}}{\text{Total number of responses}} = \frac{25}{70} \]
Now, we simplify the fraction \(\frac{25}{70}\). To do this, we find the greatest common divisor (GCD) of 25 and 70, which is 5. We can then divide both the numerator and the denominator by 5:
\[ \frac{25 \div 5}{70 \div 5} = \frac{5}{14} \]
Thus, the empirical probability of David's incorrect responses in simplest form is:
\[ \frac{5}{14} \]