1. 5/6(42х/10-6у/5)-54/10(2х/9-15у/10) =(23х+71у)/10
а. 5*42х/6*10=1*7х/1*2=7х/2
б.5*6у/6*5=1*у/1*1=у
в. 54*2х/10*9=6*х/5*1=6х/5
г. 54*15у/10*10=27*3у/5*2=81у/10
д. 7х/2-у-6х/5+81у/10= (7х/2-6х/5) +(81у/10-у) =((5*7х - 6х*2)/10 + (81у-10*у)/10) = (35х-12х)/10 + 71у/10 = (23х+71у)/10