Step 1: Concept
Let the number of dimes Jessica has = J
Step 2: 
Less than mean that you will subtract.
Step 3:
7 times the number of dimes Jessica has = 7J
Step 4: 
4 less than 7 times the number of dimes Jessica has is 
 7J - 4
Step 5: Final answer
7J - 4
Option B