$\left \{ {{4x-5=3y} \atop {2x-y=3}} \right.$
`<=>` $\left \{ {{4x-5=3y} \atop {y=2x-3}} \right.$
`<=>` $\left \{ {{4x-5=3(2x-3)} \atop {y=2x-3}} \right.$
`<=>` $\left \{ {{4x-5=6x-9} \atop {y=2x-3}} \right.$
`<=>` $\left \{ {{-2x=-4} \atop {y=2x-3}} \right.$
`<=>` $\left \{ {{x=2} \atop {y=1}} \right.$
Vậy hệ pt có 1 nghiệm duy nhất `(x;y) = (2;1)`