aanswer now! pls oh pls

Answer: 25
Step-by-step explanation:
If two shapes are similar , then the ratio of their sides are also similar.
From the shapes given:
[tex]\frac{x}{50}[/tex] = [tex]\frac{20}{40}[/tex]
[tex]\frac{x}{50}[/tex] = [tex]\frac{1}{2}[/tex]
2x = 50
x = 25