In the picture, we see two similar triangles, this means that ther is a factor k which satisfies:
h = 6k
and
40 = 10k
Isolating k in each equation:
[tex]\begin{gathered} \frac{h}{6}=k \\ \frac{40}{10}=k \end{gathered}[/tex]
This means that:
[tex]\begin{gathered} \frac{h}{6}=\frac{40}{10} \\ or\text{ equivalently} \\ \frac{6}{h}=\frac{10}{40} \end{gathered}[/tex]
