Ming's at-risk amount at the end of the year is $23,425.
The at-risk amount in an investment is the amount a taxpayer can potentially lose in that investment.
It is used to determine the deductible loss for tax purposes.
The formula for calculating the at-risk amount is:
At-Risk Amount=Initial Investment+Additional Contributions−Withdrawals−Allocable Share of Losses
In this case, Ming's initial investment is $46,850, he has taxable income of $4,685 from the oil partnership, and he withdraws $18,740.

So, Ming's at-risk amount at the end of the year is $23,425.