bonjour
K = 1/8 - 7/12 : 7/6 + 7/12
= 1/8 - 7/12 x 6/7 + 7/12
= 1 /8 - 42/ 84 + 7/12
= 1/8 - 1/2 + 7/12
= 3/24 - 12/24 + 14/24
= 5/24
M = ( 1/8 + 7/12) : ( 5/6 - 4/15 )
= ( 3/24 + 14/24) : ( 25/30 - 8/30)
= 17/24 : 17/30
= 17/34 x 30/17 = 510/578
= 15/17