5y+7(3-y)=3(5-2y)-6-это первый. 7y-4(3y+5)=2-3(4y-9)

5y+7(3-y)=3(5-2y)-6 5y+21-7y=15-6y-6 5y-7y+6y=15-6-21 4y= -12 y=-12:4 у= - 3     7у-4(3у+5)=2-3(4у-9) 7у-12у-20=2-12у+27   7у-12у+12у=20+2+27 7у= 49 у=49:7 у=7     

[latex]5y+7(3-y)=3(5-2y)-6[/latex]   [latex]5y+21-7y=15-6y-6[/latex]   [latex]21-2y=9-6y[/latex]   [latex]6y-2y=9-21[/latex]   [latex]4y=-12[/latex]   [latex]y=-12:4[/latex]   [latex]y=-3[/latex] ________________________________________________________________ [latex]5\cdot(-3)+7\cdot(3-(-3))=3\cdot(5-2\cdot(-3))-6[/latex] (это проверка)   [latex]-15+7\cdot(3+3)=3(5+6)-6[/latex]   [latex]-15+7\cdot6=3\cdot11-6[/latex]   [latex]-15+42=33-6[/latex]   [latex]27=27[/latex] ============================================================= [latex]7y-4(3y+5)=2-3(4y-9)[/latex]   [latex]7y-12y-20=2-12y+27[/latex]   [latex]-5y-20=29-12y[/latex]   [latex]12y-5y=29+20[/latex]   [latex]7y=49[/latex]   [latex]y=49:7[/latex]   [latex]y=7[/latex] ___________________________________________________________ [latex]7\cdot7-4\cdot(3\cdot7+5)=2-3\cdot(4\cdot7-9)[/latex]   [latex]49-4\cdot(21+5)=2-3\cdot(28-9)[/latex]   [latex]49-4\cdot26=2-3\cdot19[/latex]   [latex]49-104=2-57[/latex]   [latex]-55=-55[/latex]