20i + 5i = 25i B
when a number has an "I" in it it is an imaginary number. You get an imaginary number by taking a square root of a negative number. (or other even index root) For example: sqrt-4= +-2i
You would add and subtract these just like any other like terms. 20x + 5x = 25x
Where imaginary numbers differ is when !multiplying and dividing. i * i = -1
I hope this helps.