Once a student attempts a question, they are provided with a fully worked out solution. For minor mistakes, this is usually enough guidance for the student to figure out how to solve the next time.
In this example, the student had 2 attempts to calculate the angle ABC, but didn't get it right.
The worked solution appears on the right, going through each step of the calculation. There is also a reference to the theorems that are needed for the calculation.
This immediate feedback allows a student to see where they went wrong. If they have previously mastered the earlier concepts in this topic, this feedback is often enough to enable the student to solve similar problems next time.
Engagement: getting questions wrong with no clear explanation of why is often a big demotivator. By having immediate access to the worked solution, students feel encouraged to figure it out and try again.