To solve for \( y \) in the equation
\[ \frac{ey}{n} + k = t, \]
we start by isolating \( \frac{ey}{n} \):
- Subtract \( k \) from both sides:
\[ \frac{ey}{n} = t - k. \]
- Next, multiply both sides by \( n \):
\[ ey = n(t - k). \]
- Finally, divide both sides by \( e \):
\[ y = \frac{n(t - k)}{e}. \]
So, the correct answer is:
\[ c \quad y = \frac{n(t - k)}{e}. \]