you mean 'y' intercept not 'why' intercept
y intercet means where the line crosses or intersepts the y axis
that also is when x=0
bsically, y intercept point is (0,yintercept)
in this graph , the y intercept is 3 units below the 0 so y intercept is -3 at point (0,-3)
y=mx+b
b=y intercept
we want to find an equation that is
y=mx-3
convert them into that
(1) y=(12-6x)/4
y=-3/2x+3
nope
(2)
27+3y=6x
subtract 27
3y=6x-27
divide 3
y=2x-9
nope
(3)
6y+x=18
subtract x
6y=-2x+18
'divide 6
y=-1/3x+3
nope
(4)
y+3=6x
subtract 3
y=6x-3
correct
answer is number 4