Determine whether the quadrilateral is a parallelogram. justify your answer.
a) yes; opposite angles are congruent.
b) yes; opposite sides are congruent.
c) yes; diagonals bisect each other.
d) no; opposite sides are not congruent.

Luke started a weight-loss program. the first week, he lost x pounds. the second week, he lost pounds less than times the pounds he lost the first week. the third week, he lost 1 pound more than of the pounds he lost the first week. liam started a weight-loss program when luke did. the first week, he lost 1 pound less than times the pounds luke lost the first week. the second week, he lost 4 pounds less than times the pounds luke lost the first week. the third week, he lost pound more than times the pounds luke lost the first week.