Answer:
12. standard deviation =6.22972...
. variance = 38.80952...
Let x be the unknown number
2x +7 = 39
2x+7-7 = 39-7
2x = 32
2x/2 = 32/2
x=16
You use the balance method to solve. First, you cancel the +7 by subtracting the 7 ON BOTH SIDES to balance the equation.. After that, you are left with 2x, where you will need to isolate the x by dividing by 2 ON BOTH SIDES to balance it.
Hope this helps
The answer for your question is A.
X=10
YEAR 4: $1316.09 -- decreased $16683.91
YEAR 5: $684.37 -- decreased $631.72
YEAR 6: $355.87 -- decreased $328.50
YEAR 7: $185.05 -- decreased $170.82
YEAR 8: $96.23 -- decreased $88.82
The averages of the decreases is equal to 304.97, so the second one is the answer.