Answer :

[tex]\frac{12}{15}\\\\divide\ a\ numerator\ and\ a\ denominator\ by\ 3\\\\12:3=4;\ 15:3=5\\\\therefore\ \frac{12}{15}=\frac{4}{5}\\\\multiply\ a\ numerator\ and\ a\ denominator\ by\ 2\\\\4\cdot\ 2=8;\ 5\cdot2=10\\\\therefore\ \frac{12}{15}=\frac{4}{5}=\frac{8}{10}=\boxed{0.8}\Rightarrow0.8\cdot100\%=\boxed{80\%}[/tex]



[tex]\frac{68}{80}\\\\divide\ a\ numerator\ and\ a\ denominator\ by\ 4\\\\68:4=17;\ 80:4=20\\\\therefore\ \frac{68}{80}=\frac{17}{20}\\\\multiply\ a\ numerator\ and\ a\ denominator\ by\ 5\\\\17\cdot\ 5=85;\ 20\cdot5=100\\\\therefore\ \frac{68}{80}=\frac{17}{20}=\frac{85}{100}=\boxed{0.85}\Rightarrow0.85\cdot100\%=\boxed{85\%}[/tex]
kate200468
[tex] \frac{\big{12}}{\big{15}}= \frac{\big{3\cdot4}}{\big{3\cdot5}}= \frac{\big{4}}{\big{5}}= \frac{\big{4\cdot2}}{\big{5\cdot2}}= \frac{\big{8}}{\big{10}}=0.8 \\\\1\%\ \ \rightarrow\ \ 0.01\ \ \ \ \ \ \Rightarrow\ \ \ \ \ 10\%\ \ \rightarrow\ \ 0.01\cdot10=0.1\\\\0.8=8\cdot0.1 \ \rightarrow\ \ 8\cdot10\%=80\%\\\\--------------------\\\\ [/tex]

[tex]\frac{\big{68}}{\big{80}}=\frac{\big{4\cdot17}}{\big{4\cdot20}}=\frac{\big{17}}{\big{20}}=\frac{\big{17\cdot5}}{\big{20\cdot5}}=\frac{\big{85}}{\big{100}}=0.85\\\\0.85=0.8+0.05=8\cdot0.1+5\cdot0.01\\\\0.85\ \ \rightarrow\ \ 8\cdot10\%+5\cdot5\%=80\%+5\%=85\%[/tex]