How do you round the number 26.778 give me the result

Can someone me out here number 4 plz

Elizabeth claims that the fourth root of 2 can be expressed as 2^m since (2^m)^n = 2. find the values of m and n for the case where elizabeth's claim is true.

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.