稀里糊涂

He explained the arithmetic problem twice, but I was none the wiser.

The rules and regulations muddled me completely.

Without a second thought I agreed to take the job.

This is a serious matter. It shouldn't be handled in a perfunctory manner.

My father looked casually through my school report.

He muddled along carelessly day by day.

have a perfunctory discussion

make a superficial inspection

give one's careless approval/consent