If a figure is to be a parallelogram, then opposite angles must be congruent. Therefore, if one angle in the figure measures x degrees, then the opposite angle must also measure x degrees. The remaining two angles in the figure will also be congruent to each other, and their measures will depend on the measures of the first two angles. If the first two angles each measure x degrees, then the remaining two angles will also each measure x degrees. If the first two angles each measure y degrees, then the remaining two angles will also each measure y degrees.