The parallel lines have created similar triangles. So, the following is true:
[tex] \frac{20}{30} = \frac{AC}{AE} = \frac{2}{3} [/tex]
this means that [tex] \frac{CE}{AE} = \frac{1}{3} [/tex]
Because those sides are shared we can create the following proportion:
[tex] \frac{1}{3} = \frac{4}{h} [/tex]
Cross - multiply and we get h = 12
