In the given parallelogram ABCD:
CD=5x-18
BC=3x-6
AB=2x+12
From the properties of parallelogram: The opposite sides of parallelogram are equal
Pair of opposite sides are:
AB & CD
BC & DA
Opposite sides are equal:

x = 10
Substitute the value of x = 10 in the expression of BC
BC = 3x - 6
BC = 3(10) - 6
BC = 30 - 6
BC = 24
Opposite sides are equal: BC = DA
BC = 24 = DA
DA = 24
Answer: DA = 24