[tex]\displaystyle\bf\\7)\\\\A=\Big\{x\Big|x\in N,~x<7\Big\}\\\\A=\Big\{0;~1;~2;~3;~4;~5;~6\Big\}\\\\\\B=\Big\{x\Big|x\in N,~3\leq x<8\Big\}\\\\B=\Big\{3;~4;~5;~6;~7\Big\}\\\\\\C=\Big\{x\Big|x\in N,~7~\vdots~x\Big\}\\\\~~~~~~~D_7=\{1;~7\}\\\\C=\Big\{1;~7\Big\}\\\\\\D=\Big\{x\Big|x\in N,~x+3=4\Big\}\\\\x+3=4\\x=4-3\\x=1\\\\D=\Big\{1\Big\}\\\\\\E=\Big\{x\Big|x\in N,~x-1=2\Big\}\\\\x-1=2\\x=2+1\\x=3\\\\E=\Big\{3\Big\}[/tex]
