4-0.5(х+9)=2.1 4-0,5х-4,5=2,1 4-0.5х=2.1+4.5 4-0.5х=6.6 0.5х=4-6.6 0.5х=-2.2 х=-2.2:0.5 х=-22:5 х=-4.4 Ответ:-4.4