**7/72**

Total possibilities = 6x6x6=216

With first die being 1 there are 6 possible ways of having 8, (1,1,6/1,2,5/1,3,4/1,4,3/1,5,2/1,6,1)

With 2- 5 ways,

With 3- 4 ways,

with 4- 3 ways,

with 5- 2 ways,

With 6- 1 way

Total number of ways = 6+5+4+3+2+1=21

**Probability = 21/216 = 7/72**