Question

What is the approximate percent decrease when a fish count goes down from 850 to 500?

Answer 1

So, the count went down from 850 to 500, or 350 units.

if we take the 850 to be the 100%, what is 350 in percentage off of it?

$\bf \begin{array}{ccllll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 850&100\\ 350&x \end{array} \implies \cfrac{850}{350}=\cfrac{100}{x}$

solve for "x".