Answer: 6.93 years
Step-by-step explanation:
Given
Rate of interest is 
Future value is given by 
For the investment to double itself, i.e. 

It takes around 6.93 years to double the investment.
Simply the answer is 12 and 8.
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1. 3h+11
2. -2r
3. g-4
4. 5f+4
5. 15z
The angle next to the angle 5x is 180 - 5x
All angles sum to 360
(6x - 58) + (2x + 4) + (180 - 5x) = 180
3x + 126 = 180
3x = 54
x = 18
For question 10, sum of angles in pentagon is 540 degrees
x + 105 + 85 + 114 + 126 = 540
x + 430 = 540
x = 110