x^m means x times itself m times
(-6)^5 means -6 time itself 5 times
simplify it says
remember that
(mn)^x=(m^x)(n^x)
undistribute the -1
(-6)^5=(-1)^5 times (6^5)
(-1)^5=-1 since it is odd power
can be simplified to
-6^5
(note, -6^5 vs (-6)^5 PEMDAS)