The percentage change in Corey's average in math is -5.21%
Here, we want to get the percentage of change
Mathematically, we can use the formula below;
[tex]\frac{new\text{ value - old value}}{\text{old value}}\text{ }\times100[/tex]From the question, the new value is 91, while the old value is 96
Substituting these values in the equation above, we have;
[tex]\begin{gathered} \frac{91-96}{96}\times100 \\ \\ =\text{ }\frac{-5}{96}\times100 \\ =\text{ -5.21} \end{gathered}[/tex]