76 * (1 / 23-1 / 53) + 23 * (1 / 53 + 1 / 76) + 53 * (1 / 23-1 / 76), please explain the reason, thank you!

76 * (1 / 23-1 / 53) + 23 * (1 / 53 + 1 / 76) + 53 * (1 / 23-1 / 76), please explain the reason, thank you!

76*(1/23-1/53)+23*(1/53+1/76)-53*(1/23-1/76)
=76/23-76/53+23/53+23/76-53/23+53/76
=(76/23-53/23)-(76/53-23/53)+(23/76+53/76)
=1-1+1
=1