Calculate the hydrogen-ion concentration [h+] for the aqueous solution in which [oh-] is 1 x 10-11 mol/l. is this solution acidic, basic, or neutral? show your work

You can use the fallowing equations:
pH=-log[H⁺]
pH=14-pOH
pOH=-log[OH⁻]
[H⁺]=K(w)/[OH⁻]    (K(w)=1.01×10⁻¹⁴)

You can use any of those equation in what ever order to find the [H⁺] and then pH.  If pH>7, the solution is basic.  If the pH<7, the solution is acidic.

I will show you how I would find it but there is more than one way to do it.
[H⁺]=(1×10⁻¹⁴)/(10⁻¹¹)
[H⁺]=0.001M
pH=-log(0.0010)
pH=3.00
Therefore the solution is acidic.

I hope this helps.  Let me know in the comments if anything is unclear.

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.