Answer:
Quadrilateral ABCD is a <u>parallelogram</u> when value of x is <u>4</u> and y is <u>4.</u>
Step-by-step explanation:
Given:
Length of AB = 
Length of DC = 16
Length of AD = 
Length of BC = 
Also Given:
In quadrilateral ABCD, we can say opposite sides are AB and DC and other Opposite sides are BC and AD.
hence we can check both for both equality
Length AB = Length of DC
Substituting the values we get;

when x=4
Length of AB =
which is equal to Length of DC
Also for other pair;
Length BC = Length of AD
Substituting the values we get;

Hence Length of AD = 
Length of BC = 
Hence Length of AD = Length of BC
Since both pairs of opposite sides are congruent.
Hence, Quadrilateral ABCD is a <u>parallelogram</u> when value of x is <u>4</u> and y is <u>4.</u>