# Chapter 5 - Ratio and Proportion - 5.4 Solving Problems - 5.4 Exercises: 9

$x=91$

#### Work Step by Step

We are given the proportion $\frac{42}{x}=\frac{18}{39}$. We can set the cross products equal to each other and solve for the unknown variable. $42\times39=x\times18$ $1638=18x$ Divide both sides by 18. $x=91$

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