Chapter 5 - Number Theory and the Real Number System - 5.3 The Rational Numbers - Exercise Set 5.3 - Page 285: 74

$\dfrac{ 1 }{ 6 }$

To combine fractions, make sure that the fractions have the same denominators before combining their numerators. \begin{align} \dfrac{ 7 }{ 12 } - \dfrac{ 5 }{ 12 } &= \dfrac{ 7 - 5 }{ 12 } &&\text{Subtract the numerators} \\ &= \dfrac{ 2 }{ 12 } \\ &= \dfrac{ 2 \div 2 }{ 12 \div 2 } &&\text{Reduce to lowest terms} \\ &= \boxed{ \dfrac{ 1 }{ 6 } } \end{align}