4/9*(9/2y-3/2)-2/7*(7/6-7/2y)
4/9*(9/2y-3/2)-2/7*(7/6-7/2y)=4/9*9/2у-4/9*3/2-2/7*7/6+2/7*7/2у=2у-2/3-1/3+у=3у-1
4/9*(9-3y)/2y-2/7(7y-21)=2/9y*(9-3y)-2(y-3)=2/3y*(3-y)+(3-y)/3y=(3-y)/y