Đáp án:
Đặt `{9x-13}/16={7y-11}/19={z-5}/3=k`
`=>`$\left\{\begin{matrix} \dfrac{9x-13}{16}=k\\ \dfrac{7y-11}{19}=k\\ \dfrac{z-5}{3}=k \end{matrix}\right.$`=>`$\left\{\begin{matrix} x=\dfrac{16k+13}{9} \\ y=\dfrac{19k+11}{7}\\ z=3k+5 \end{matrix}\right.$
Có `5x-7y+3z=9`
`<=>5cdot{16k+13}/9-7cdot{19k+11}/7+3(3k+5)=9`
`<=>80/9k+65/9-19k-11+9k-15`
`<=>{-10}/9cdotk={-20}/9`
`<=>k=2`
`=>x={16cdot2+13}/9=5`
`y={19cdot2+11}/7=7`
`z=3cdot2+5=11`