287. Упростите: а) 0,2(2,1x - 2,3y) - 0,4(3,1y + 1,9x); б) 4/15(1 2/3 n - 4,5) - 1 1/2(8/27 n + 5,4).

а) \(0.2(2.1x-2.3y)-0.4(3.1y+1.9x)=0.42x-0.46y-1.24y-0.76x=-0.34x-1.7y\).

б) \(\frac4{15}\left(\frac53n-4.5\right)-\frac32\left(\frac8{27}n+5.4\right)=\frac49n-1.2-\frac49n-8.1=-9.3\).

Ответ: а) \(-0.34x-1.7y\); б) \(-9.3\).