$\"\"$

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a.

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There are $\"\"$ people playing tennis in a park.

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Some are playing doubles and some are playing singles.

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Let $\"\"$ be the number of doubles matches.

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Let $\"\"$ be the number of singles matches.

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There are $\"\"$ matches in progress.

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The equation is $\"\"$ .

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A doubles match requires $\"\"$ players and a singles match requires $\"\"$ players.

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The equation is $\"\"$ .

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

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$\"\"$

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b.

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Find how many matches of each kind are in progress.

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Solve the equation.

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$\"\"$ (First equation)

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

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

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Substitution method:

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$\"\"$ (Second equation)

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

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

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$\"\"$ (Combine like terms)

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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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$\"\"$ (Cancel common terms)

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Find the $\"\"$ value.

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$\"\"$ (Simplified first equation)

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

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$\"\"$ (Subtract: $\"\"$ )

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Therefore, there are $\"\"$ doubles matches and $\"\"$ singles matches are in progress.

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$\"\"$

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There are $\"\"$ doubles matches and $\"\"$ singles matches are in progress.