A line equation can be written in slope intercept form, which is
[tex]y=mx+b[/tex]Where m represents the slope and b the y-intercept.
For our first problem, we have a line that passes through the point (0, 8) and has a slope equals to 3.
If we substitute this slope value on the form presented, we're going to have
[tex]y=3x+b[/tex]If we evaluate our point on this form, we're going to find our missing coefficient b.
[tex]8=3\cdot0+b\Rightarrow b=8[/tex]The line equation with slope equals to 3 that passes through (0, 8) is
[tex]y=3x+8[/tex]