x - y = 1
2x + 3y = 12
2x + 3y = 12 passes through (6, 0) and (0, 4)
x – y = 1 passes through (1, 0) and (0, -1)

Coordinates of the vertices of the triangle formed with the y axis are (0, 4), (0, -1) and (3, 2)
Base of the triangle = 4 + 1 = 5
Height of the triangle = 3
Area of the triangle = \(\frac{1}{2}\) x base x height
⇒ Area of the triangle = \(\frac{1}{2}\) x 5 x 3