Question

The pH of a solution at 25°C in which [OH–] = 3.8 x 10–5 M is....

Answer 1

You used the concentration of hydroxide ions [OH-] rather than the concentration of hydronium ions [H3O+] there, which gives you pOH rather than pH.

To convert into pH, though, it is a simple matter of using the relationship:
pH + pOH = 14, where we found pOH = 4.42
pH + 4.42 = 14
Where it is simply algebra to solve for pH.

Answer 2

omg i just relized what i did...

Answer 3

i guess i read too fast just thought they gave me the H30+ concentration