(1/12-1/13)-(1/10-1/11) решите по действиям

1) 1/12 - 1/13 = 1*13/12*13 - 1*12/13*12 = 13/156 - 12/156 = 1/156
2) 1/10 - 1/11 = 1*11/10*11 - 1*10/11*10 = 11/110 - 10/110 = 1/110
3) 1/156 - 1/110 = 1*110/156*110 - 1*156/110*156 = 110/17160 - 156/17160 =
= - 46/17160 = - 23/8580