[tex]a) \frac{1}{2}+ \frac{2}{5} + \frac{5}{2}= \frac{5*1}{5*2}+ \frac{2*2}{2*5} + \frac{5*5}{2*5} = \frac{5}{10} + \frac{4}{10} +\frac{25}{10} = \frac{34}{10}= \frac{17}{5}
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[tex] b)\frac{2}{9} +\frac{13}{10} + \frac{7}{9} + \frac{17}{10} = \frac{2*10}{9*10}+ \frac{9*13}{9*10} + \frac{10*7}{10*9} + \frac{9*17}{9*10}= \frac{20}{90}+ \frac{117}{90}+ \frac{70}{90} + \frac{153}{90} = \frac{360}{90} = \frac{36}{9} =4[/tex]
[tex]c) \frac{1}{7}+ 0+ \frac{7}{8} + \frac{8}{7}= \frac{1}{7} + \frac{8}{7} + \frac{7}{8} = \frac{9}{7} +\frac{7}{8} = \frac{8*9}{8*7} + \frac{7*7}{7*8} = \frac{72}{56} + \frac{49}{56} = \frac{121}{56} [/tex]
