1
[tex] \left \{ {{a+b=17} \atop {a=b+17}} \right. \\ \left \{ {{b+17+b=17} \atop {a=b+17 \\
[/tex]
[tex] \left \{ {{2b=0} \atop {a=b+17}} \right. \\ \left \{ {{b=0} \atop {a=17}} \right. [/tex]
2
[tex] \left \{ {{a-b=12} \atop {a=4b}} \right. \\ \left \{ {{4b-b=12} \atop {a=4b}} \right. \\ \left \{ {{3b=12} \atop {a=4b}} \right. \\ \left \{ {{b=4} \atop {a=16}} \right. [/tex]
3
[tex] \left \{ {{x+y=450} \atop { \frac{x}{y} = \frac{1}{4} }} \right. \\ \left \{ {{x+y=450} \atop {y=4x}} \right. \\ \left \{ {{x+4x=450} \atop {y=4x}} \right. \\ \left \{ {{5x=450} \atop {y=4x}} \right. \\ \left \{ {{x=90} \atop {y=360}} \right. [/tex]
