[tex]\it \left.\begin{aligned}\it d|7x+4 \Rightarrow d|(7x+4)\cdot9 \Rightarrow d|63x+36\\ \\ \it d|9x+5 \Rightarrow d|(9x+5)\cdot7 \Rightarrow d|63x+35\end{aligned}\right\} \Rightarrow d|63x+36-63x-35 \Rightarrow d=1[/tex]
