Identify the graph of 3i (see figures).

Any complex number can be written in fallowing form:
Z = x + yi

When drawing complex numbers as point on x,y coordinate system we can use variables x and y to represent our coordinates in x y coordinate system.

Our complex number is:
Z = 3i which means
x = 0 and y = 3
x is real part of complex number and we draw it on x axis (real number axis) and y is imaginery part and we draw it on y axis (imaginery axis)

answer is point with coordinates (0,3) Graph 1