why can i divide the numbers in part b to grt the direct answer of 13.02% but in part C i have to put to the power of 0.5 to grt the answer of 12.01%? where does that 0.5 come from? please explain as simply as you can

6) fa, 1 (1+z2) (1+fail) = (1+2)3 ( 1 A: 2 B:3 3 1.37 -> 2,1 -13.021. - 13.021. 1.21 47f1,2 : (1+z) (Itfip) = (1+2)3 TAI (109)' (1+f1, 2) = (1.1) 11,2 = (12.011.) (1.37 es B:3 ) = 0. 4 | ( h 64