So there is a real and imaginary axis the midopint is just the average of them average between the reals is (5-3)/2=2/2=1 average between imaginaries is (18i+2i)/2=20i/2=10i
A rectangle is a parallelogram because its pairs of opposite sides are parallel. A rectangle also has the characteristic that all of its angles are right angles; all four of its angles are congruent.