5/6*(42/10х-11/5y)-54/10*(2/9x-15/10y)=
5/6*42/10x-5/6*11/5y-54/10*2/9x-5+54/10*15/10y=
7/2x,-11/6y-6/5x+81/10y=
-16/10x+94/15y
(180:18+8)*6=(10+8)*6=18*6=108
(135:9+14)*2=(15+14)*2=29*2=58
(16*5-20):15=(80-20):15=60:15=4
(4*80-280)*4=(320-280)*4=40*4=160
(78+27):7*3=105:7*3=15*3=45
(840-730)*3:11=110*3:11=330:11=30
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