Answer: 2
Step-by-step explanation:

I think it's the first 7.
I hope this helps :-)
Its already fully simplified.
Answer:
18
Step-by-step explanation:
1) Simplify the expression
-1 + 10 + 9
9 + 9
18
51.5 Hectograms + 5100 Grams
51,500 Decigrams = 5100 Grams
They have same mass because they equal each other.