To find out how many french fries Ravi had left after giving some to his friends, we start with the total number of fries he had, which is 61.
He gave away 14 french fries to each of his \( f \) friends. Thus, the total number of french fries given away is \( 14f \).
To find out how many french fries he had left, we need to subtract the total given away from the original amount:
\[ 61 - 14f \]
However, looking at the options provided, we can simplify and match them to our expression.
The correct expression that corresponds to this situation is: D. \( 61 - f \times 14 \)
So the answer is D.