要不你自己去一趟吧。

Why don't you go yourself.

快跑吧，要不就迟到了。

Run quickly, otherwise you'll be late.

事情大概很紧要，要不他哪里会夜里打电话来

it must be very important, otherwise he wouldn't have called in the middle of the night

详细点讲吧，要不会有许多地方不清楚

give a bit more detail, or else many areas will be unclear

要不他来，要不我去。

Either he'll come or I'll go.