[tex]\frac{3}{10}-\frac{1}{4}\\\\find\ LCD(\frac{3}{10};\ \frac{1}{4})\\\\List\ the\ multiples\ of\ 10:0;\ 10;\ \fbox{20};\ 30;...\\\\List\ the\ multiples\ of\ 4:0;\ 4;\ 8;\ 12;\ 16;\ \fbox{20};\ 24;...\\\\LCD(\frac{3}{10};\ \frac{1}{4})=\fbox{20}\\\\\frac{3}{10}=\frac{3\cdot2}{10\cdot2}=\frac{6}{20};\ \frac{1}{4}=\frac{1\cdot5}{4\cdot5}=\frac{5}{20}\\\\therefore:\\\\\frac{3}{10}-\frac{1}{4}=\frac{6}{20}-\frac{5}{20}=\frac{6-5}{20}=\boxed{\frac{1}{20}}[/tex]
