You write 100 as the denominator because 100 represents a whole whereas the numerator normally represents a percentage. Hope this helps!
I think the answer is -48°F
Then its 0. something. but not a whole number :) hope this helped
Double angle (or half angle, depending how you look at it) identities:



So we have



Note that when taking the square root, we should take into account that that could yield two possible solutions, but we know
and
, so it's also the case that
.
Also, the reason we have equality in the last step can be explained like so:

(not unlike the process used to complete the square)
6/25 or 6 over 25, however you wanna look at it!