3384 because .88 times 1800 is 1584 and you have to add that to 1800 making it 3384 (or the questions is really easy and its just 1800.88)
How you write 8.216 in scientific notation; 8.216 * 10 ^ 3
10 ^ 3 = 10 to the 3rd power.
Because they show exactly how much of something is there/needed.
The answer is 49 because it is
