Вычислите : а) 1/65 + 7/130 - 9/13 б) 15/34 - 5/51 + 16/17 в) 17/36 + 13/12 + 11/18 г)...

Решите задачу:

$\frac{1}{65}+ \frac{7}{130} - \frac{9}{13} = \frac{2}{130}+ \frac{7}{130}- \frac{90}{130}= \frac{9}{130}-\frac{90}{130}=- \frac{81}{130}; \\ \frac{15}{34}- \frac{5}{51}+ \frac{16}{17}=\frac{15}{2*17}- \frac{5}{3*17}+ \frac{16}{17}= \frac{45}{102} - \frac{10}{102}+ \frac{96}{102}= \frac{131}{102}= \\ =1 \frac{29}{102} ;$

$\frac{17}{36}+ \frac{13}{12} + \frac{11}{18}= \frac{17}{36}+ \frac{39}{36}+ \frac{22}{36}= \frac{78}{36}=2 \frac{6}{36}=2 \frac{1}{6} ; \\ \frac{25}{48}- \frac{9}{16}- \frac{21}{80}= \frac{25}{3*16}- \frac{9}{16}- \frac{21}{16*5}= \frac{125}{240}- \frac{135}{240} - \frac{63}{240}= \\ = \frac{73}{240}$