6(2/5) - 8(5/8)

= 12/5 - 40/8

= 12/5 - 20/4

= (124)/(54) - 20/4

= 48/20 - 20/4

= 48/20 - 100/20

= (48 - 100)/20

= -52/20

= -13/5

Ответ: -13/5