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I'm not sure how to explain it
You have to divide the 3 because 6&9 have 3 in common which will leave you with square root a^2 c^3.
The unit rate is the slope
y=mx+b
m=slope
b=y intercept
equation is y=7x
slope=7
y intercept=0
slope=unit rate because if you use 5 gasoline then you go 5 times 7 miles or 35 miles
The unit rate is 7
Hope I helped :)
To simplify this:

You can factor the denominator and then cancel out some terms. But, this is not factorable. So, I think you are missing a term or you wrote this wrong.