The expression we have is:

And we are given values for d and f:

The first step will be to substitute these values into the expression
Step 1. Substituting d=9 and f=8 into the given expression:

Step 2. Simplify the multiplications.
9(9) is equal to 81 and 4(8) is equal to 32, thus:

Step 3. The last step is to subtract 81-32:

This result is shown in option b.
Answer:
b) 49