Percent ionization help.?

Question

Hydroxylamine, HONH2, like ammonia, is a Bronsted base. A 0.15 M solution has a pH of 10.12. I was able to calculate the Kb value to be 1.2E-7 and the pKb to be 6.94, however I keep getting 0.088 % ionization which is incorrect. If anyone could help me out, I would be very grateful.

Answer 1

pOH=14-pH= 14-10.12 =3.88
Kb=x^2/(0.15-x) = ((10^-3.88)^2)/(0.15-10^-3.88) = 1.16 *10^-7= 1.3*10^-7 So you have calculated Kb correctly.

The degree is a=x/C= (10^-3.88)/0.15 =0.00088 = 0.088%

I get the same. Why is it incorrect?
Maybe they ask you to find the a for a different C?