Answer:
x = 21
Step-by-step explanation:
If ΔABC and ΔAED are similar (AAA), then coresponding sides are in proportion.
[tex]\dfrac{AB}{AE}=\dfrac{AC}{AD}=\dfrac{BC}{ED}[/tex]
We have
[tex]AB=15,\ BC=x,\ AE=45,\ ED=63[/tex]
Substitute:
[tex]\dfrac{15}{45}=\dfrac{x}{63}[/tex] cross multiply
[tex]45x=(15)(63)[/tex]
[tex]45x=945[/tex] divide both sides by 45
[tex]x=21[/tex]
