# Chapter 5 - Number Theory and the Real Number System - 5.3 The Rational Numbers - Exercise Set 5.3: 79

$\dfrac{ 9 }{ 10 }$

#### Work Step by Step

To combine fractions, make sure that the fractions have the same denominators before combining their numerators. \begin{align} \dfrac{ 3 }{ 4 } + \dfrac{ 3 }{ 20 } &= \dfrac{ 15 }{ 20 } + \dfrac{ 3 }{ 20 } &&\text{Make equivalent fractions} \\ &= \dfrac{ 15 + 3 }{ 20 } &&\text{Add the numerators} \\ &= \dfrac{ 18 }{ 20 } \\ &= \dfrac{ 18 \div 2 }{ 20 \div 2 } &&\text{Reduce to lowest terms} \\ &= \boxed{ \dfrac{9}{10} } \end{align}

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