## Thinking Mathematically (6th Edition)

$x=5$ ft
Similar triangles have corresponding sides that are proportional. The corresponding sides in the similar triangles are: the 8-ft and the 4-ft sides the 10-ft side and the one marked with an $x$. Use proportions to obtain: $\dfrac{8}{4} = \dfrac{10}{x}$ Cross-multiply to obtain: $8x=4(10) \\8x=40 \\x = \frac{40}{8} \\x=5$