Answer:
8000
Step-by-step explanation:
It's the only number missing from the answer to arrive at the answer itself :)
8,000
70 + x + 8 + 800,000,000 = 800,008,078 Add on the left side
800,000,078 + x = 800,008,078
-800,000,078 - 800,000,078 Subtract 800,000,078 from both sides
x = 8,000
