Hi Peter,
Yes, you can do this from the Homework Sets Editor. Find the set, and click the link in the "Edit Assigned Users" column. On the page which loads up you'll see links to "Edit data for So-and-So." Then, for the particular problem you want to give credit for, change the "Status" to 1 (for 100%).
Hope this helps,
Jason
WeBWorK Main Forum
Manually Changing a Student Grade
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