Using voltage divider to regulate voltage to a device
Like many things, technically you can if you’re willing to make certain compromises but practically it would never make sense.  Since the load applied by your laptop could vary significantly with workload, perhaps from less than 1W to 60W or more, and you’d need to keep within the voltage limits of the laptop (guessing 11 to 14V) you’d need a resistive divider that presents 14V at zero load but still 11V at 5A.  Even without working out the exact values you’d need it’s clear that you would have to draw much more than 5A from the supply and the divider would dissipate well over 100W in addition to the laptop’s load.  So if you found yourself in a disaster movie and had a massive 20V PSU, miles of nichrome wire and a laptop and needed to crack Dr Evil’s launch codes then you could do it, but in almost any other situation you wouldn’t.