Answer:
20 longs, 9 units more than the 9 flats
Step-by-step explanation:
If Abby has 9 flats, she has 900 blocks of the 1109 she needs. The remaining 209 can be represented by ...
20 longs
9 units
_____
Comment on the question
We cannot see the model Abby has put together so far, so we don't know exactly what it takes to finish it. Any longs or units she already shows must be subtracted from the numbers above.
