Note, a watt-hour is a watt-hour. The laptop's battery capacity is 42 W-hr, while the example power bank's would most likely be 111 W-hr. Assuming we're charging at a rate of 1C (so laptop's capacity in one hour), we basically need to drive 42W into the laptop battery.
42W out of the power bank would be 11.34A at 3.7V, though that amperage is worryingly high (to put in perspective, the maximum coming out of your typical home outlet is around 12-15A). Also you need to boost the voltage up anyway because batteries need to be charged at a slightly higher voltage than it outputs. So for simplicity's sake, let's say the battery needs 14V to charge. That drops it down to 3A. Much more doable. And if it were generating an AC output, that drops it down further to less than half an amp.
This is all under ideal scenarios obviously.
In any case, you'd be able to charge the laptop around 2 times since the power brick isn't just charging the laptop.