This line has an equation

3x + 4y + c = 0,     (1)


where "c" is some constant, now unknown.


To find "c", use the condition that y-intercept is 2.

It means that the point (x,y) = (0,2) lies on the line (1), i.e.

3*0 + 4*2 + c = 0,


which gives you the value of c = -8.