To solve for \( v \) in the equation
\[
- \frac{3v}{8} = -18, \]
first, we can eliminate the negative signs from both sides:
\[ \frac{3v}{8} = 18. \]
Next, we will multiply both sides by 8 to get rid of the fraction:
\[ 3v = 18 \times 8. \]
Calculating the right side:
\[ 18 \times 8 = 144, \]
so we have:
\[ 3v = 144. \]
Now, divide both sides by 3:
\[ v = \frac{144}{3}. \]
Calculating the division gives:
\[ v = 48. \]
Thus, the solution is
\[ \boxed{48}. \]