0.00067=67X10^5 so
67X10^5-2.3X10^5
64.7X10^5 which can be expressed as:
6.47X10^6
(not sure if it matters to you or not, but technically we only had two significant figures so it should be rounded to 6.5X10^6)
Answer:
c is the correct answer..........
Step-by-step explanation:

While subtracting , the sign of each term of second expression changes & remove the parentheses.
⟶ 
Combine like terms. Like terms are those which have the same base. Only coefficients of like terms can be added or subtracted.
⟶ 
⟶ 
In standard from , the expression should be written in such a way that the power of variables goes from highest to lowest.

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Answer:
x = 15
Step-by-step explanation:
Pytago: a^2 + b^2 = c^2
x =
= 15