So you are asked to solve the equation .

Basically, you solve this like you would any equation. Multiply on both sides by z+ i: . Subtract (1+ 2i)z from both sides: iz- (1+2i)z= (-1- i)z= -2+ i. Divide both sides by -1-i: . You can "rationalize" the denominator of that fraction by multiplying both numerator and denominator by the conjugate of -1- i.