Question

What is the y-intercept of the line whose equation is y = x - 3?

Answer 1

Hello : 
the y-intercept of the line whose equation is y = x - 3
when ; x=0 : y =0-3 =-3

Answer 2

Because you are using the format y = mx +c the c value is the y offset.

in this equation the equation can be rewritten as y = 1x -3

Thus the y intercept, the y offset, must be -3.

Hope this helps! :)