\large \Large \frac{\frac{2}{7}-\frac{1}{2}}{3-\frac{3}{4}}\large
\large =- \Large \frac{3}{21}\large
\large =- \Large \frac{2}{21}\large
\large =- \Large \frac{2}{20}\large
\large =- \Large \frac{1}{21}\large