So for this, we will be putting the equation in slope-intercept form, which is [tex] y=mx+b [/tex] , with m = slope and b = y-intercept (aka the point in which the line crosses the y-axis)
Since it's stated that -2 is our slope, this means that -2 is the m variable.
Since it's also stated that the y-intercept is (0,3), 3 is our b variable.
Putting our equation together, it's [tex] y=-2x+3 [/tex]