Hey there mate!
So, when doing this kind of notation (scientific notation), this is pretty much like braking down the number,and trying to make it more simple.

I hope this helps you! :)
Answer:
1000?
Step-by-step explanation:
1200+480+920 =2600
3600-2600 = 1000?
maybe
3:6 3,6,9 6,12,18,24
9:24. ~~ ~~
Yes it is equivalent because if you divide 9:24 with 3 it will equal 3:6 and if you keep adding with 3:6 buy it's self it will eventually aqualung 9:24