Consider the given equation.
x−y+1=0
⇒y=x+1
3x+2y−12=0
⇒y=6−3x2
Consider the graph shown below.
Point (2,3) is the point of intersection. So, it is the solution of both the equations.
Now, at x-axis, y=0. So,
x−0+1=0
⇒x=−1
3x+0−12=0
⇒x=4
Therefore, coordinates of the vertices of the triangle formed by both the lines and the x-axis are (2,3),(−1,0) and (4,0).