Consider the given figure, in the triangle ADE and ABC,
Angle A is common in both the triangles.
Already given that angle ADE is equal to angle ABC.
Consider the property that the sum of all three angles of a triangle is 180 degree,

Therefore, by the AAA criteria, the triangles ADE and ABC are similar.
Then the sides of the triangle are proportional,

This can also be written as,

This is the required answer.