Answer:
y = 2x
Step-by-step explanation:
In the equation y = mx, m represents the slope of the line.
The slope can be calculated as:

Where (x1, y1) and (x2, y2) are the coordinates of two points in the line.
So, replacing (x1, y1) by (1, 2) and (x2, y2) by (2, 4), we get:

Therefore, the equation of the line is:
y = 2x