Question

What is the graph of `6x+3y=18`?

Answer 1

The graph is a straight line. This is a linear equation and you can write it in the form (isolating `y` on one side):
`y=-6/3x+18/3`
or
`y=-2x+6`

Observing your equation you can see
`-2` which is the slope of your line, and tells you that is decreasing (as `x` increases `y` decreases); and `6` that is the intercept on the `y` axis.
So:
if `x=0` then `y=6`
if `x=1` then `y=4`

if `y=0` then `x=3`

Graphically: