\((4.2\times10^8)+(5.9\times10^9)\\~\\ =\,(4.2\times\frac{10}{10}\times10^8)+(5.9\times10^9)\\~\\ =\,(4.2\times\frac{1}{10}\times10\times10^8)+(5.9\times10^9)\\~\\ =\,(0.42\times10^9)+(5.9\times10^9)\\~\\ =\,10^9\times(0.42+5.9)\\~\\ =\,10^9\times6.32\\~\\ =\,6.32\times10^9\\~\\ =\,6,320,000,000\)
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