0.5*(0.7х+0.9)- 0.4* (0.3х-0.6)= - 0.9*(0.3х+0.9)

0.35х+0.45-0.12х+0.24= -0.27х-0.81

0.35х-0.12х+0.27х= -0.81-0.24-0.45

0.5х= -1.5

х= -1.5: 0.5

х= -3