Question

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Answer 1

Let N be the nickels and Q be the quarters, since Charlie found 35 coins, we can write

$\begin{gathered} N+Q=35 \\ or\text{ equivalently} \\ N=35-Q \end{gathered}$

Now, we know that a nickel is worth 5 cents and a quarter is worth 25 cents, then we can write

$\begin{gathered} 5N+25Q=100\times5.15 \\ 5N+25Q=515 \end{gathered}$

Then, the answer is option a.