# Chapter 6 - Section 6.2 - Integrated Review - Ratio, Rate, and Proportion - Page 430: 38

$x = 18$

#### Work Step by Step

We use the method of cross multiplying, which states that if $\frac{a}{b} = \frac{c}{d}$, then $ad = bc$. This result can be achieved by multiplying both sides by $cd$. $\frac{21}{x} = \frac{\dfrac{7}{2}}{3} \rightarrow \frac{7}{2}x = 63 \rightarrow\frac{7}{2} \cdot \frac{2}{7} \cdot x = 63\cdot \frac{2}{7} \rightarrow x = 18$

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