Solutions by everydaycalculation.com
640 - 1440 is -15.
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 12/40-14/40 6/40-28/40 6/80-14/40 6/40-14/80 18/40-14/40 6/40-42/40 30/40-14/40 6/40-70/40 42/40-14/40 6/40-98/40
© everydaycalculation.com