Richard did not suggest using Add on the Datepicker.
As this is an assignment I will not give you the code, but here are the steps to follow and some reference material you may find useful
1. Create a
DateTime
variable
2. Assign the Date value from the first DatePicker to that variable
3. Extract the number of weeks from the TextBox - you might find
Int32.TryParse Method (System)/a>[^] useful
4. Multiply the number of weeks by 7 to get the number of days to add
5. Use the
datetime.adddays[
^] to add the results from step 4 to the variable you populated in step 2
6. Assign the value of the results of step 5 to the second datepicker