(-1 3/8- 2 5/12):5 5/12

(-1 3/8 - 2 5/12) : 5 5/12 = - 7/10

1) - 1 3/8 - 2 5/12 = - ( 1 9/24 + 2 10/24) = - 3 19/24
2) - 3 19/24 : 5 5/12 = - 91/24 : 65/12 = - 91/24 * 12/65 = - (7*1)/(2*5) = - 7/10 

Пояснения:
 3/8 = 9/24 - доп.множ.3
5/12 = 10/24 - доп.множ.2
3 19/24 = (3*24+19)/24 = 91/24
5 5/12 = (5*12+5)/12 = 65/12