Always because every opposite side of the parallelogram has similar angles
350 x 15 = 5,250
5, 250 divided by 1000 is 5.25
15% = 5.25
if the price was marked up 15% the price would be
$ 360.25 >> 350 + 5.25
if the price was marked down 15% , the price will be $ 344.75
