Answer:
33.3333% decrease
Step-by-step explanation:
Percent change formula: [tex]\frac{(x-y)}{|y|} *100[/tex], where x is the new value and y is the starting value.
Plug in values and solve:
[tex]\frac{20-30}{30} *100\\\frac{-10}{30} *100\\-0.3333*100\\[/tex]
-33.3333% change, or a 33.3333% decrease.