774*(1/723+1/51)-723*(1/51-1/774)-51*(1/723-1/774)
=774/723+774/51-723/51+723/774-51/723+51/774
=(774/723-51/723)+(774/51-723/51)+(723/774+51/774)
=723/723+51/51+774/774
=1+1+1
=3