x - the percent decrease
[tex]60-60x=39 \ \ \ |-60 \\
-60x=-21 \ \ \ |\div (-60) \\
x=\frac{-21}{-60} \\ \Downarrow \\ x=\frac{-21}{-60}=\frac{-21 \div (-3)}{-60 \div (-3)}=\frac{7}{20}=\frac{7 \times 5}{20 \times 5}=\frac{35}{100}=35\%[/tex]
It's a 35% decrease.
