To evaluate the function \( c(x) = 2.5x + 15 \) for \( x = 10 \), we'll substitute \( 10 \) into the function:
\[ c(10) = 2.5(10) + 15 \]
Now, calculating \( 2.5 \times 10 \):
\[ 2.5 \times 10 = 25 \]
Next, we add \( 15 \):
\[ 25 + 15 = 40 \]
Therefore,
\[ c(10) = 40 \]
The answer is:
40