Final answer:
The equation of the line is y = -2x + 3.
Step-by-step explanation:
The equation of a line can be written in the form y = mx + b, where m is the slope and b is the y-intercept. In this case, the slope is given as -2 and the line crosses the y-axis at (0, 3). This means that the y-intercept is 3. So, the equation of the line is y = -2x + 3.