-0,3(1-3a)+4(0,2n-0,1)-(0,1-0,7n), если n= 0,21
-0.3+0.9а+0.8n-0.4-0.1+0.7n=1.5n+0.9a-0.8=1.5*0.21+0.9a-0.8=-0.485+0.9a