a) -5/9+8/15+ -2/11+4/-9+7/15
=-5/9+8/15+ -2/11-4/9+7/15
=-5-4/9+8/15+-2/11+7/15
=-5-4/9+(8+7)/15+. -2/11
=-9/9+. (8+7)/15+. -2/11
=-9/9+15/15+. -2/11
=-1+15/16+. -2/11
=-1 +1 +-2/11
=0+. -2/11
=-2/11
b)(7/2.5/6)+(7/6:2/7)
=35/12+(7/6:2/7)
=35/12+49/12
=7
a)<
b)=