To evaluate the expression \( 23.9g + 36 \) for \( g = -1.1 \), we substitute \(-1.1\) for \( g \):
\[ 23.9(-1.1) + 36 \]
First, calculate \( 23.9 \times -1.1 \):
\[ 23.9 \times -1.1 = -26.29 \]
Now, add \( 36 \) to \(-26.29\):
\[ -26.29 + 36 = 9.71 \]
Thus, the value of the expression \( 23.9g + 36 \) for \( g = -1.1 \) is:
\[ \boxed{9.71} \]