Clara writes the equation open paren x minus 13 close paren times open paren x plus 8 close paren is equal to 196 to solve for the missing side length of a rectangle represented by the factor x plus 8 What is the missing side length represented by x plus 8 units of the rectangle?

Solve (x − 13)(x + 8) = 196. Expanding and rearranging gives x² − 5x − 300 = 0, which factors as (x − 20)(x + 15) = 0. Since a side length must be positive, x = 20, so the side represented by x + 8 is 20 + 8 = 28 units. The correct choice is 28.

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