It's N=9 it's really confusing but trust me it N
Arithmetic sequences have a common difference between consecutive terms.
Geometric sequences have a common ratio between consecutive terms.
Let's compute the differences and ratios between consecutive terms:
Differences:

Ratios:

So, as you can see, the differences between consecutive terms are constant, whereas ratios vary.
So, this is an arithmetic sequence.
66.5cm
Split the shape into a square and triangle and find the area separately
Square: 8*7=57
Triangle: 7*3/2 = 10.5
=66.5
Surface of a cubical box=6(side²)
1)We have to calculate the surface of this cubical box.
Rate=cost of painting / surface ⇒surface=cost of painting/rate
Data:
Rate=$15/m²
cost of painting=$1440
Surface=$1440/($15/m²)=96 m²
2)We find out the length of the side:
Surface of a cubical box=6(side²)
Data:
Surface of a cubical box=96 m2
Therefore:
96m²=6 (side²)
side²=96 m²/6
side²=16 m²
side=√(16 m²)=4 m
3) We find the volume of a cubical box.
volume=(side³)
volume=(4 m)³
volume=64 m³
Answer: the volume of this cubical box would be 64 m³.