a) \[ 776 \cdot 10^{-6} = 7.76 \cdot 10^2 \cdot 10^{-6} = 7.76 \cdot 10^{-4} \]
б) \[ 0.00773 \cdot 10^{21} = 7.73 \cdot 10^{-3} \cdot 10^{21} = 7.73 \cdot 10^{18} \]
Ответ: а) 7.76 ⋅ 10-4; б) 7.73 ⋅ 1018