Wolfram alpha result - https://www.wolframalpha.com/input?i=arcsin+%28arccos+%28arc...

3pi - 9

= 0.42477796076937971538793014983850865259150819812531746292483377692344921885

This is the result if you do it in radians, but the test actually requires that you set the calculator to degrees mode first.

Note that all of the inverse trig functions are multivalued because the trig functions are periodic. Here, Wolfram Alpha is giving you one of the possible answers. The entire family of answers should be +/-9 + n*pi for any integer n; the sign on the 9 is due to cos being an even function.