1. In the equation $\overline{x 5} \cdot \overline{3 y} \bar{z}=7850$, restore the digits $x, y, z$
Since $\overline{x 5}$ is a factor of 7850, in $x=$ $0,1, \cdots, 9$, $x$ can only be 2. (If $x=0$, then $5 \cdot 400=2000<7850$, if $x=1, 3, 4, \cdots$, 
9, then $\overline{x 5}$ cannot divide 7850.) Therefore, $\overline{3 y z}$ $=7850 \div 25=314$, which means $y=1, z=4$.