Answer:
37.5 units
Step-by-step explanation:
I assume that there is condition: BC║DE . If so, then ΔABC ~ ΔADE ⇒ that corresponding sides are proportional.
[tex]\frac{BC}{DE}[/tex] = [tex]\frac{AC}{AE}[/tex]
AC = 30 + 20 = 50
[tex]\frac{x}{15}[/tex] = [tex]\frac{50}{20}[/tex] ⇒ x = [tex]\frac{15*50}{20}[/tex] = 37.5 units
