gucwin

log(x)=ln(x)/ln(10)

261.6:392=2616:3920 and 2616=2*2*2*109 (109 is prime number) 3920=2*2*2*2*5*7*7 261.6:392=109/490 - as simple as possible Is it helpfull?

109 is prime number, so it's impossible to simplify it more.

x-lifespan 1/3*x+1/6*x+12+y+1/6*x=x since y is "half the remainder of his time", it means it's equal 1/6*x solving the equation: x=72 USA - 24 years India - 12 years Egypt - 12 years So the answer is EGYPT.

2E12 means 2*10^12 , so your calculation is correct

I have been using scientific notation for like 20 years, so I don't remember how I get that, sorry...

"3xexponent4" means "3*x*exp(4)"?