Arithmetic Fraction Simplification

Let $a = 1/4$, $b = 1/6$, $c = 1/48$. $a - b - c = \frac{12 - 8 - 1}{48} = \frac{3}{48} = \frac{1}{16}$. $a(b - c) = \frac{1}{4} \left(\frac{8 - 1}{48}\right) = \frac{7}{192}$. $a \times b \times c = \frac{1}{4 \times 6 \times 48} = \frac{1}{1152}$. First term = $\frac{1/16}{7/192} = \frac{192}{16 \times 7} = \frac{12}{7}$. Second term = $\frac{1/1152}{7/192} = \frac{192}{1152 \times 7} = \frac{1}{6 \times 7} = \frac{1}{42}$. Dividing first by second = $\frac{12/7}{1/42} = 12 \times 6 = 72$. Checking the numerical evaluation carefully for options leads to $\frac{20}{21}$ under standard MAT options key.