[tex]a) \frac{6}{1} + \frac{7}{1} = \frac{13}{1} = 13[/tex]
[tex]b) \frac{9}{1} - \frac{8}{1} = \frac{9 - 8}{1} = \frac{1}{1} = 1[/tex]
[tex]c) \frac{213}{210} = \frac{213 \div 3}{210 \div 3} = \frac{71}{40} [/tex]
[tex]d) \frac{ \frac{n}{1} }{( \frac{n}{1} - \frac{2}{1}) } = \frac{ \frac{n}{1} }{n - \frac{2}{1} } = \frac{ \frac{n}{1} }{n - 2} = \frac{n}{n - 2} [/tex]
[tex]e) \frac{( \frac{n}{1} - \frac{3}{1} )}{( \frac{n}{1} - \frac{5}{1}) } = \frac{n - \frac{3}{1} }{ \frac{n}{1} - \frac{5}{1} } = \frac{n - 3}{ \frac{n}{1} - \frac{5}{1} } = \frac{n - 3}{n - \frac{5}{1} } = \frac{n - 3}{n - 5} [/tex]
[tex] \frac{1}{ \frac{n}{1} } - \frac{1}{( \frac{n}{1 } + \frac{2}{1}) } = \frac{1}{n} - \frac{1}{n + \frac{2}{1} } = \frac{1}{n} - \frac{1}{n + 2} = \frac{n + 2 - n}{n \times (n + 2)} = \frac{2}{n \times (n + 2)} = \frac{2}{n {}^{2} + 2n} [/tex]
