(17/15 - 1/12) 20/3 = (34/30 - 5/60) 20/3
= (68/60 - 1/12) 20/3
= (68/60 - 5/60) 20/3
= 63/60 20/3
= 21/20 20/3
= 1/3

Ответ: 1/3