[tex] \frac{2 + n}{5 - n } = 2 \frac{1}{2} \\ \frac{2 + n}{5 - n} = \frac{5}{2} \\ 2(2 + n) = 5(5 - n) \\ 4 + 2n = 25 - 5n \\ 7n = 21 \\n = \frac{21}{7} \\ n = 3[/tex]
