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.
Standard form: -3x +5y= -1
Given, (0,−2).
Since the x-coordinate is 0, the point clearly lies on y-axis.
Also, the y-coordinate −2 being negative, the point lies on the negative y-axis.