We know that the area of a triangle is half of that of a parallelogram if they are on the same base and between the same parallels.
In case triangle XCB, base is half. Therefore, area of triangle XCB
= 1/2 x 1/2 ar(ABC)
Now ar(AXCD) = ar(ABCD) - ar(XCB)
= 1 - 1/4
As area of AXCD is 3/4ar(ABCD), area of ABCD
= 24 x 4/3
We know that a diagonal divides a parallelogram into two triangles of equal area.
Thus area of ABC = 1/2 ar(ABCD)
or, ar(ABC) = 1/2 x 32
or, ar(ABC) = 16cm²
Hope that helps !!