You divide the shape into smaller shapes you can calculate, like rectangles and triangles. If the shape is irregular, you have to approximate, for example by dividing it into many narrow rectangles. This technique is called "integration".
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You would find the area of the inside and outside shape (pretending that the inside shape was not in the outside shape). then, you would take the area of the outside shape and subtract the area of the inside shape.
Shape of what ?
Assuming "liths" is an unusual way of spelling lengths, you cannot because a quadrilateral is not a rigid shape. It can be deformed into a quadrilateral with the same sides but a different area. This can be illustrated by thinking of a square deforming into a rhombus. Same sides but different area.
To find the area, first divide the shape into regular, simple shapes. Then use formulas to find the area of the smaller, regular shapes. Lastly, add up all the smaller areas to find the area of the original shape.
Such as? If you can break the shape up into triangles you can find the area that way. Or, you can get into calculus-based equations if you have an equation for the random shape.