2100*0,7*(0-х)=4200*2.5*(5-0)+3.35*10^5*0.064
0-x=(4200*2.5*5+3.35*10^5*0.064)/2100*0.7
-x=(52500+21440)/1470
-x=73940/1470=7394/147
x=7394/147