A laptop only works for about 30 minutes on a full charge, while the same model has the battery life of more than 3 hours. To solve the problem, what should you do first?

Small devices often have abnormally short battery lives. If it's a laptop, you might be able to calibrate the battery. For all mobile devices, consider totally draining the battery and then fully charging it before turning the device back on. If none of these measures work, the battery will most likely need to be replaced.