Final answer:
The expression that represents how big the peach is after 5 weeks is x * 32.
Step-by-step explanation:
To write an expression that represents how big the peach is after 5 weeks, we need to consider that the peach doubles in size every week. So, after the first week, it will be twice its original size, after the second week, it will be four times its original size, and so on. We can represent this using exponential notation. Let's call the original size of the peach 'x'. After 5 weeks, the peach will be 2^5 times its original size.
Therefore, the expression that represents how big the peach is after 5 weeks is x * 2^5 or x * 32.