The cost to paint a is 12/13 square feet per dollar.
The unitary method is a method for solving a problem by the first value of a single unit and then finding the value by multiplying the single value.
Jacob spends 13/4 dollars to paint 9/3 square feet.
[tex]\dfrac{\dfrac{9}{3}}{ \dfrac{ 13}{4}} = \dfrac{9}{3} \times \dfrac{ 4}{13}\\\\= \dfrac{ 36}{39}\\\\= \dfrac{ 12}{13}[/tex]
Hence, the cost to paint a is 12/13 square feet per dollar.
Learn more about the unitary method;
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