Chapter 8 - Applications of Trigonometric Functions - 8.2 The Law of Sines - 8.2 Assess Your Understanding - Page 530: 3

$\dfrac{15}{2}$

If two triangles are similar then their sides are proportional: $\dfrac{a_1}{a_2}=\dfrac{b_1}{b_2}=\dfrac{c_1}{c_2}$ Hence, for the given similar triangles, \begin{align*}\dfrac{3}{2}&=\dfrac{x}{5}\\ 5\cdot\dfrac{3}{2}&=\dfrac{x}{5}\cdot 5\\ \dfrac{15}{2}&=x\end{align*}