13.89%
The value of the first die can be any number except for 1 because even if the second die rolls a 6, the total will only be 7. This means that there is a 5/6 chance of rolling an appropriate number with the first die. The second die has a 1/6 chance of rolling any given number. Any given number can be added to only one of the five numbers from the previous die to equal an 8. As a result, both numbers must be multiplied.
5/6 x 1/6 = 5/36 or 13.89%
