The number that you are thinking of is 4. To get this answer I did the opposite of how you received your answer.
40 - 12 = 28
28 ÷ 4 = 7
The number that you are thinking of is 4.
25*2=50
10*5=50
so 2 packets of envelopes and 5 packets of stamps
Answer:
Required center of mass 
Step-by-step explanation:
Given semcircles are,
whose radious are 1 and 4 respectively.
To find center of mass,
, let density at any point is
and distance from the origin is r be such that,
where k is a constant.
Mass of the lamina=m=
where A is the total region and D is curves.
then,

- Now, x-coordinate of center of mass is
. in polar coordinate 




![=3k\big[-\cos\theta\big]_{0}^{\pi}](https://tex.z-dn.net/?f=%3D3k%5Cbig%5B-%5Ccos%5Ctheta%5Cbig%5D_%7B0%7D%5E%7B%5Cpi%7D)
![=3k\big[-\cos\pi+\cos 0\big]](https://tex.z-dn.net/?f=%3D3k%5Cbig%5B-%5Ccos%5Cpi%2B%5Ccos%200%5Cbig%5D)

Then, 
- y-coordinate of center of mass is
. in polar coordinate 




![=3k\big[\sin\theta\big]_{0}^{\pi}](https://tex.z-dn.net/?f=%3D3k%5Cbig%5B%5Csin%5Ctheta%5Cbig%5D_%7B0%7D%5E%7B%5Cpi%7D)
![=3k\big[\sin\pi-\sin 0\big]](https://tex.z-dn.net/?f=%3D3k%5Cbig%5B%5Csin%5Cpi-%5Csin%200%5Cbig%5D)

Then, 
Hence center of mass 
Answer:
the second one because 3 divided by 1.5 is 2 then it's right
Median is just the middle number. If you put all the numbers in order from least to greatest:
4,5,6,7,8,9,10
Then you can find the one in the middle. In this case it’s 7.