Let $t$ be TNYWR.

Gray has $t$ dollars consisting of $\$ 1$ and $\$ 2$ coins. If she has the same number of $\$ 1$ and $\$ 2$ coins, how many $\$ 1$ coins does she have?

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Let $k$ be the number of $\$ 1$ coins that Gray has. It is given that $k$ is also the number of $\$ 2$ coins, which means the total amount of money in dollars that Gray has is

$$
k(1)+k(2)=k(1+2)=k(3) .
$$

The answer to (a) is 12 . Therefore, $\$ 3 k=\$ t$ so $k=\frac{t}{3}=\frac{12}{3}=4$.