[tex]\displaystyle\bf\\16)\\\\a)~~\overline{7x}=\overline{y8}\implies x=8;~y=7\\\\b)~~\overline{xx}=\overline{y2}\implies x=2;~y=x=2\\\\c)~~\overline{5y7}<\overline{50x}\implies y=0;~x_1=8;~x_2=9\\\\d)~~\overline{2xy}>\overline{289}\implies x=9;~y\in\{0,1,2,3,4,5,6,7,8,9\}\\\\e)~~\overline{72x398}<\overline{724y28}\implies x\in\{0,1,2,3\};~y\in\{0,1,2,3,4,5,6,7,8,9\}[/tex]