If activity A has a period of 10 days and activity B has a duration of 7 days with a 2- day lag, what is the overall duration of both activities combined, given a start-to-start relationship with a supposition that both activities will start as soon as possible?

In a start-to-start relationship, the successor activity (activity B) must wait for its predecessor (activity A) to start before it can start. Since both activities are beginning as soon as possible, we can assume that activity B will begin immediately after activity A starts. However, there is a lag of two days, meaning that activity B must wait two days to start after activity A has started. That means that from the moment that A starts, activity B will not be completed until nine days have passed (just add the duration of the activity, plus the two day lag). Since the activities overlap in this scenario, then the duration that has passed for both activities to finish will have been 10 days total.