Let's denote the other rational number as x. We know that the sum of the two rational numbers is -8. Therefore, we can write the equation:
-17/9 + x = -8
To find the value of x, we need to isolate it on one side of the equation. Let's solve for x:
x = -8 + 17/9
To add the fractions, we need to find a common denominator. The common denominator for 9 and 1 is 9. So, let's rewrite the equation with a common denominator:
x = (-8 * 9/9) + 17/9
x = (-72/9) + 17/9
Now, we can combine the numerators:
x = (-72 + 17)/9
x = -55/9
Therefore, the other rational number is -55/9.