翻译：经过三整天的努力，他们终于找到了电脑瘫痪的原因。(work out)

After the effort for three days,they have worked out why the computer broke down finally.

经过三整天的努力，他们终于找到了电脑瘫痪的原因
After three day-long endeavor, they had found the computer paralysis reason finally

After three whole days' of hard work, they finally worked out the reason for the paralysed computer.

After all three days' effort, they finally worked out the dead reason of the computer.