How many quarters does she have?

Janice has $2.30 made up of dimes, pennies and quarters. She has as many dimes as pennies and she has 17 coins in all. How many quarters does she have?

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x = number of pennies
x = number of dimes  {she has as many dimes as pennies}
17 - 2x = number of quarters  {subtracted dimes and pennies from total number of coins}

x + 10x + 25(17 - 2x) = 230  {value of a coin times number of coins equals total value}
11x + 425 - 50x = 230  {used distributive property}
-39x + 425 = 230  {combined like terms}
-39x = -195  {subtracted 425 from each side}
x = 5  {divided each side by -39}
17 - 2x = 7  {substituted 5, in for x, into 17 - 2x}

She has 7 quarters.

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