\[\frac{\frac{7}{3} - \left(1 + \frac{1}{2} - \frac{1}{4}\right)}{\frac{5}{3} - \left(6 - \frac{21}{4} + \frac{1}{6}\right)} = \frac{\frac{7}{3} - \frac{5}{4}}{\frac{5}{3} - \frac{11}{12}} = \frac{\frac{13}{12}}{\frac{9}{12}} = \frac{13}{9}\,.\]
7/3-(1+1/2-1/4) = 7/3-(4+2-1)/4 = 7/3-5/4 = (28-15)/12 = 13/12
5/3-(6-21/4+1/6) = 5/3-(72-63+2)/12 = 5/3-11/12 = (20-11)/12 = 9/12
13/12*12/9 = 13/9