Question

A man bought a car for $8,200 and sold it for 80% of the price two years later. How much did he lose?
The difference between number 20 and its opposite is what percentage of 200? (if you do not remember: opposite of 15 is −15; opposite of −7 is 7.)

Answer 1

OK so 80% of 8,200=6560

8,200-6560= 1,640

He lost 1,640

Answer 2

if we take 8200 as the 100%, then  $\bf \begin{array}{ccllll} amount&\%\\ \textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\ 8200&100\\ x&80 \end{array}\implies \cfrac{8200}{x}=\cfrac{100}{80}\implies \boxed{?} \\\\\\ \textit{so, the man lost }8200-\boxed{?}$
solve for "x"



well, the opposite of 20, will then be -20, their difference is then (20) - (-20)

how much is that amount of 200 in percentage? well, if we take 200 as the 100%

then    $\bf \begin{array}{ccllll} amount&\%\\ \textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\ 200&100\\ (20)-(-20)&x \end{array}\implies \cfrac{200}{(20)-(-20)}=\cfrac{100}{x}$

solve for "x"