$\"\"$

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Let $\"\"$ be the number of T-shirts.

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Let $\"\"$ be the number of hats.

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Observe the table:

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The cost and sale price of each item is shown.

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The boosters spend a total of $\"\"$ on T-shirts and hats.

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The total selling price on T-shirts and hats make $\"\"$ .

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Find how many T-shirts did they sell.

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Cost price: $\"\"$ .

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Sales price: $\"\"$ .

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The system of equations is $\"\"$ and $\"\"$ .

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Solve the equations and find the $\"\"$ value.

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$\"\"$ (Cost price)

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$\"\"$ (Subtract $\"\"$ from each side)

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$\"\"$ (Apply additive inverse property: $\"\"$ )

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$\"\"$ (Divide each side by $\"\"$ )

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$\"\"$ (Divide each side by $\"\"$ )

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$\"\"$

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Find the $\"\"$ value.

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$\"\"$ (Sales price)

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Distributive property: $\"\"$ )

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$\"\"$ (Subtract $\"\"$ from each side)

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$\"\"$ (Apply additive inverse property: $\"\"$ )

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$\"\"$ (Multiply each side by $\"\"$ )

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$\"\"$ (Multiply)

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Therefore, they sold $\"\"$ T-shirts.

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$\"\"$

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They sold $\"\"$ T-shirts.