You just set up the ratio like this and solve:
Answer:
A Complex Number is a combination of a
Real Number and an Imaginary Number
and
Imaginary numbers, also called complex numbers, are used in real-life applications, such as electricity, as well as quadratic equations. In quadratic planes, imaginary numbers show up in equations that don’t touch the x axis. Imaginary numbers become particularly useful in advanced calculus.
Angle D is 40 because Angle A and D are the corresponding angles since the triangles are congruent.
Hope this helps :)