Kat has 19 coins, all quarters and dimes, that are worth a total of $4. The system of equations that can be used to find the number of quarters, q, and the number of dimes, d, she has is shown.q + d=190.25q + 0.1d=4

The first equation says q + d = 19, so d = 19 − q. Substitute that into the value equation: 0.25q + 0.10(19 − q) = 4. Simplifying gives 0.15q = 2.10, so q = 14. Kat has 14 quarters, which is choice C.

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