Answer
China: $1.2 \ billion $
US: $ .47 \ billion $
Work Step by Step
We are told that 11% of the population lives in China and 4.5% of the population lives in the US. Multiplying the percents as decimals by the total population, we find the population of each country:
China:
$$ = .11 \times 10.5 \ billion \\ = 1.2 \ billion $$
US:
$$ = .045 \times 10.5 \ billion \\ = .47 \ billion $$