Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 Patrick has 4 hours less than twice the amount of time that Greg has left to finish his homework. Greg has six hours less than Jacob left to finish his homework. If Jacob has 18 hours left to finish his homework, calculate the total number of hours they all have left to finish their homework?


### Response:
 如果Jacob还有18小时完成作业，Greg还有18-6 = <<18-6=12>>12小时完成作业。
Patrick比Greg剩下的时间少4小时，即剩下的时间是12*2-4 = <<12*2-4=20>>20小时。
总共，他们还有12+20+18 = <<12+20+18=50>>50小时完成作业。