Tính

a ) 3 14/19 + 13/17 + 35/43 + 6 5/19 + 8 /43
b ) -5/7 . 2/11 + -5/7 . 9/11 + 1 5/7
 c)11 3/13 - (2 4/7 + 5 3/13 
d ) 2/7 . 5 1/4 - 2/7 .3 1/4