The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept
We have the slope [tex]m=-3\to y=-3x+b[/tex]
and point (4, 2). Substitute:
[tex]2=-3(4)+b[/tex]
[tex]2=-12+b[/tex] add 12 to both sides
[tex]14=b\to b=14[/tex]
Answer: [tex]y=-3x+14[/tex]