(3,0)
1) Let's make two t-tables, one for each equation so that we can find the points of each line.
2)
3x+y=9
x|y =9 -3x
-1| y= 9 -3(-1) =12
0| y = 9-3(0) = 9
1| y= 9 -3(1) =6
So we've got the points: (-1,12), (0,9) and (1,6)
Now, let's pick the second equation and rewrite it in the Slope-intercept form:
x=y+3 ⇔-y=3-x ⇔ y=x-3
x|y
-1| y=-1-3=-4
0| y= 0-3 = -3
1| y= 1-3 =-2
So, we've got the points (-1,-4), (0,-3) and (1,-2)
2.2) Let's plot those points and check:
Note that both lines intercept each other at point (3,0) and that is the solution.