Final answer:
The expression that can be used to find the total number of desserts made for the baking competition is 7 * 9.
Step-by-step explanation:
To find the total number of desserts made for the baking competition, we can use the expression a) 7 * 9.
This is because there are 7 people who each made 9 desserts. Multiplying the number of people (7) by the number of desserts made by each person (9) gives us the total number of desserts made for the baking competition.
Therefore, the correct expression is a) 7 * 9.