(1/2+1/5):2-3/10=
(3/4-5/12)*8+1/18=
(7/15+4/5):3-1/9=
(3/7-1/21)*14-1/6=

1.1,2+1,5=2,7:2=1,35-3,10=-7.35

1)( 5+2)/10:2-3/10 = 7/10×1/2-3/10=7/20-3/10=(7-6)/20=1/20=0.05 2)(9-5)/12×8+1/18=1/3×8+1/18=48/18=8/3=2 2/3 3) 19/15×1/3-1/9=14/15-1/9=37/45 4) 8/21×14-1/6=1002/126=167/21=7 20/21