1) (-2) + 9 + (-27) : 3
=(-2) +{9 + (-9)}
=(-2)+0
=-2
2) (-2/5) - (-5/2) + 3/5
=(-2/5)-(-2/5)+3/5
=0+3/5
=3/5
3) 5/7 . 9/11 + 5/7 + 3/5
=(5/7 . 9/11) +(5/7 + 3/5 )
=45/77+46/35
=371/385
4) 1/10 - 3/5 -(-1/2)
=-1/2-(-1/2)
=0
5) -5/7 . 9/11 + -5/7 . 2/11 + 1 5/7
=-5/7 . (9/11+2/11)+1 5/7
=-5/7 . 1 + 1 5/7
=-5/7 +12/7
=7/7=1
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