3/7+5/8-1/12
=3*8 / 7*8 + 5*7 / 8*7 - 1/12
=24/56 + 35/56 - 1/12
=59 / 56 -1/12
=59*12 / 56*12 - 1*56 / 12*56
= 708/672 - 56/672
= 652/672
=163/168