This is a tricky one. Don't think this was covered in the Roger review, but in order to solve this you must do the following:
1. Take the FMV of the total interest of the incoming partner. In this case it is the $38,000
2. Subtract the FMV of the asset provided to determine the FMV of services. In this case, we subtract $20,000
3. Determine the FMV of the services provided. In this case, it would be $18,000.
4. Add the ADJUSTED basis of the asset provided, in this case $15,000 to the FMV of services provided, in this case $18,000 to determine the BASIS that the partner has.
So to summarize
FMV of TOTAL interest of incoming partner: $38,000
Less: FMV of asset provided ($20,000)
Equals: FMV of services provided: $18,000
Add: Adjusted basis of asset provided: $15,000
Equals: Partner basis $33,000
This only makes sense to me because we're breaking down what constitutes the FMV of total interest acquired in order to determine the FMV of the services provided which is the required factor, in addition to the adjusted basis of the property given, to calculate the partner's basis.