With some simple rearrangement, we can rewrite the numerator as
Then factorizing the difference of squares, 
, we end up with
Slope-intercept form:
y=mx+b
m=slope
b=y-intercept
We have this line: y=9x+3; a line parallel to this line (y=9x+3) will have the same slope; therefore m would be equal to 9 (m=9).
Data:
m=9
b=-2
y=mx+b
y=9x-2
Answer: y=9x-2
The question is kind of vague in my opinion.
the best measurement to report with the scale in my opinion would be tens of pounds. my reasoning is because the decimal place would still prove importance with numbers under one hundred. above one hundred pounds and the decimal place becomes kind of pointless.
I hope I answered your question. though i'm sorry if i didn't
