A+2b=5 3a-b=8 помогите решить систему уравнений!!!

a=5-2b 3a-b=8   3(5-2b) - b =8 a=5-2b   15-6b-b=8 a=5-2b   -7b=-7 a=5-2b   b=1 a=3

[latex]\left \{ {{a+2b=5} \atop {3a-b=8}} \right.[/latex]   [latex]\left \{ {{a=5-2b} \atop {3(5-2b)-b=8}} \right.[/latex]   [latex]3(5-2b)-b=8[/latex]   [latex]15-6b-b=8[/latex]   [latex]15-7b=8[/latex]   [latex]7b=15-8[/latex]   [latex]7b=7[/latex]   [latex]b=7:7[/latex]   [latex]b=1[/latex]   [latex]a=5-2b=5-2\cdot1=5-2=3[/latex]   [latex]\left \{ {{a=3} \atop {b=1}} \right.[/latex]   Проверка:   [latex]\left \{ {{3+2\cdot1=5} \atop {3\cdot3-1=8}} \right.[/latex]   [latex]\left \{ {{3+2=5} \atop {9-1=8}} \right.[/latex]   [latex]\left \{ {{5=5} \atop {8=8}} \right.[/latex]