Check the picture below.
if you go from the slant height, the path is shorter to the top, since the hypotenuse is the longest of all sides in a right-triangle.
that said, is shorter but is also steeper, so the lateral edge is longer but less steep and thus a bit simpler though longer, but we're only asked on which is shorter.
Remember that complementary angles add to 90 degrees.
so therefor, you can find the complement of m<A by solving
90 - 77 = A
A = 13 degrees
^^^ This explains the second part.
The compliment of a compliment can be found by subtracting the known compliment from 90 :)