вычислите :
1) х-2/3=1/18
2) 1/12+х=3/4 +1/6
3)19/20-х=1/4
4)х+3/20=7/10+1/4

х-2/3=1/18х=1/18+2/3        1/18+2/3=(1+12)/18=13/18х=13/181/12+х=3/4+1/6х=3/4+1/6-1/12          3/4+1/6-1/12=(9+2-1)/12=10/12=5/6х=5/619/20-х=1/4х=19/20-1/4           19/20-1/4=(19-5)/20=14/20=7/10х=7/10х+3/20=7/10+1/4х=7/10+1/4-3/20          7/10+1/4-3/20=(14+5-3)/20=16/20=4/5х=4/5

1) x = 2/3 + 1/18x = 13/182) 1/12 + x = 3/4 + 1/6x = 3/4 + 1/6 - 1/12x = 10/12 = 5/63) 19/20 - x = 1/4-x = 1/4 - 19/20 - x = - 14/20 x = 14/20 = 7/104) x + 3/20 = 7/10+1/4x= 7/10 + 1/4 - 3/20 x = 16/20 = 4/5