y + x = 3
does the line increase or decrease? how do i find this without graphing the line?

Decreasing

Step-by-step explanation:

y=mx+b is called slope-intercept from because it tells you the slope,m, and the y-intercept,b.

If the slope is positive then the line is increasing.

If the slope is negative then the line is decreasing.

If the slope is zero then the line is horizontal or constant.

So let's solve our equation for y:

y+x=3

Subtract x on both sides:

y=-x+3

The slope is -1.

Therefore the line is decreasing.

just a quick addition to @Freckledspots' great reply above.

y + x = 3

y = 3 - x

if we pick any random "x" value, and then pick another value larger than the one before for "x", to get a "y" value, if "y" is decreasing, the the first value of "y" will be larger, else it's increasing, let's do so, say using hmmm x = 2 and x = 7.

x = 2

y = 3 - 2

y = 1

x = 7

y = 3 - 7

y = -4

as "x" moves to the right, from 2 to 7, "y" moved down, from 1 to -4, thus is decreasing.

the solution is h=10 because you add 9 to each side of the equation.