What is the area of the region bounded by the x-axis and the lines x+y=24 and 3x-2y=12?

Please show full solution and explanation

Draw your sketch and find the intersection of the two straight lines.

The y of that intersection point is the height of your triangle.
In your head, you can see that the x-intercept of x+y=24 is (24,0) and the x-intercept of 3x - 2y = 12 is (4,0)
so you know the base length of the triangle,
the rest is very simple.