Lets look at the hours they are open from. 9 am - 4:30 pm which is 7 and a half hours a day. Now we multiply 7 1/2 by the number of days they are open, which will be 7 1/2 * 255 = 1,912.5. This means that the library is open 1,912 1/2 hours a year.
I hope I've helped! :)
we have

<u>Find the greatest common factor GCF</u>
we know that

so
The GCF is equal to 
therefore

<u>the answer is</u>
The number is 
First, multiply both sides by 1000
1000*c = w*t*c
Since c is on both sides, they would cancel each other out
1000 = w*t
Divide both sides by t.
w = 1000*t