Question

Elsie bought a video game for $85.00. If the store charges 170% of its cost for the game, how much is the store’s profit?

Answer 1

If we take 85 to be the 100%, how much is the retail price, namely the 170%?

$\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 85&100\\ x&170 \end{array}\implies \cfrac{85}{x}=\cfrac{100}{170}\implies \cfrac{85\cdot 170}{100}=x$

so the retail price is "x", thus the profit will be x - 85.