Question

Find the y-intercept of the line who's equation is Y = 3.5 x- 0.4.

Answer 1

Y-intercept is value of y when x=0.
So just plug in x=0 and solve for y;
 
y = 3.5x - 0.4
y = 3.5(0) - 0.4
y = 0-0.4
y = -0.4
   
So y-intercept is -0.4

Answer 2

$\sf y=mx+b$

m is the slope
b is the y-intercept

so that means that the y-intercept of

$\sf y=3.5x + .4$

is $\sf .4$

$\bf{\huge{\boxed{y-intercept = .4}}}$