To determine if \( y = 5 \) is a solution to the equation \( 9 = y + 1 \), we can substitute \( y \) with \( 5 \):
\[ 9 = 5 + 1 \]
Calculating the right side:
\[ 5 + 1 = 6 \]
Now we compare both sides of the equation:
\[ 9 \neq 6 \]
Since the left side does not equal the right side, \( y = 5 \) is not a solution to the equation.
The answer is no.