1. How do I write a complex number if the real part is 0?

If the real part of a complex number is 0, the number is called a pure imaginary number.

e.g. 0 + 3i = 3i which is a pure imaginary number

2. How do I write a complex number if the imaginary part is 0?

If the imaginary part of a complex number is 0, the number will be a real number.

e.g. 3 + 0i = 3 which is a real number

3. How do I know if two complex numbers are EQUAL?

Two complex numbers are only equal if the real parts are the same and the imaginary parts are the same.

e.g. If 3 + yi = x + 4i then x = 3 and y = 4