Hi there!
To find the percent of change we can use the following formula:
[tex] \frac{new - old}{old} \times 100\%[/tex]
Let's fill in our data
[tex] \frac{64 - 80}{80} \times 100\% = [/tex]
Subtract
[tex] \frac{ - 16}{80} \times 100\% = [/tex]
Divide
[tex] - 0.2 \times 100\%[/tex]
And finally multiply
[tex] - 20\%[/tex]
Hence, the percent of change is negative 20%.
~ Hope this helps you!