so, it went down from 1250 to 1000, namely 1250 - 1000 = 250.
now, if we take 1250 to be the 100%, what is 250 off of it in percentage?
[tex]\bf \begin{array}{ccll}amount&\%\\\cline{1-2}1250&100\\250&x\end{array}\implies \cfrac{1250}{250}=\cfrac{100}{x}\implies 5=\cfrac{100}{x}\implies x=\cfrac{100}{5}\implies x=20[/tex]
