Question

x+3y=-3

Answer 1

To find the y-intercept, set x to zero and solve for y:
x + 3y = 3
0 + 3y = 3
3y = 3
y = 1
y-intercept is at (0,1)

To find the x-intercept, set y to zero and solve for x:
x + 3y = 3
x + 3(0) = 3
x = 3
x-intercept is at (3,0)

Since two points defines a line, simply plot both points on a graph and draw a line through both points -- that's it, you're done.

Answer 2

And if you wanted to put it into slope intercept form,
x + 3y = -3
Subtract x from both sides.
3y = -x - 3
Divide both sides by 3.
y = -1/3x - 1