To do so please follow the steps below.
Find the problem through the “Problems” link then type the name of the problem into the “Name” search.
Then click on the problem, and unpublish it using the options menu (If the exercise is part of an assignment, it will be unavailable for that period). Note that not all problems are editable by users. If there is no 'unpublish' option, please report the issue to Gradarius support using 'report an issue' link so they can edit the problem for you or change the access rights for the content you are trying to edit.
Then go to “Reference Solutions” tab to unpublish the primary solution from the ellipses menu (unpublish -> unpublish anyway -> ok)
Make all the necessary changes to the primary solution.
Publish the primary solution from the ellipses menu.
Finally, publish the problem using the options menu.
If students have already begun solving the assignment, you may wish to correct student grades with the new reference solution in mind. To do this, go back to the exercise in the assignment then use the "Options" menu and select "Regrade".
An email that describes what occurred during the regrading process will be sent to the instructor who executed the "regrade".