America's age = 243.85 years
Further explanation
When converting units, list and multiply all the units until you find the unit you want
Time unit conversion
1 year = 365 days
1 day = 24 hours
1 hour = 3600 s
7.69 x 10⁹ seconds to years :
[tex]\tt =7.69\times 10^9~s\times \dfrac{1`hour}{3600~s}\times \dfrac{1~day}{24~hours}\times \dfrac{1~years}{365~days}\\\\=\dfrac{7.69\times 10^9}{3600\times 24\times 365}\\\\=\boxed{\bold{243.85~years}}[/tex]
