Answer: 23 years.
Step-by-step explanation: The labor productivity grows 3% per year, then the rate of growing is 1 + 0.03 = 1.03.
The equation to caclulate the years is:
[tex]y = y_{0}.(1.03)^{t}[/tex]
To double: [tex]y = 2y_{0}[/tex]
Substituing:
[tex]2y_{0} = y_{0}.(1.03)^{t}\\(1.03)^{t} = 2\\ln1.03^{t} = ln2\\t = \frac{ln2}{ln1.03}\\ t = 23[/tex]
To double the standard of living, it will take 23 years.