Area of a quadrilateral

I need to know how to work out the area of a quadrilateral with to coordinates of A(-7,0) B(2,3) C(5,0) D(-1,-6).

Would I be right in thinking I would do this:

A and C lies on the x-axis.
B and D are heights
Split as two triangles and sum (ABC +ADC)
=0.5*12*3+0.5*12*6=54

Would this be correct if not where am I going wrong?

Thanks.

what does the picture say?

What do you mean?

Quote:

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Originally Posted by andyboy179

What do you mean?

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checking your own work leads to proficiency and confidence when solving problems

So am I wrong?