Answer:
5
Step-by-step explanation:
Let the number of the kitchen clock sold =a
Let the number of the cuckoo clock sold =b
Let the number of the two-foot high grandfather clocks sold =c
The new saleswoman sold at least two of each of the three models.
Therefore:

In all, she collected $300 from selling these models alone
17a+31b+61c=300
17(2)+31(2)+61(2)=218
300-218=82
Next, we try to express the remainder (82) in terms of 17, 31 and 61
82=17(3)+31
Therefore, she sold:
- 5 kitchen clocks
- 3 cuckoo clocks
- 2 two-foot high grandfather clocks
She sold 5 $17 clocks.
CHECK:
17(5)+31(3)+2(61)=$300
We have to calculate the suface of the four walls and the ceiling.
Surface of the four walls=2(10 ft * 10ft ) + 2(12 ft * 10 ft)=200 ft² + 240 ft²=
=440 ft²
Surface of the ceiling=10 ft * 12 ft=120 ft²
Total surface=440 ft² + 120 ft²=560 ft²
Now, we have to caluclate the number of gallons of paint.
1 gallon------------------------400 ft²
x----------------------------------560 ft²
x=(1 gallon * 560 ft²) / 400 ft²=1.4 gallons.
answer: Ryan need to paint all four walls and the ceiling 1.4 gallons.