answer: 1020000
step-by-step explanation:
(7.8*10^5+(2.4*10^5) given expression
(7.8*10^5)+(2.4*10^5) group with parenthesis
(7.8+2.4)*10^5 combine like terms
10.2*10^5 preform addition
10.2*100000 evaluate the exponent
1020000 multiply out
