Here's how to calculate the pH of a solution with a given hydroxide ion concentration:

1. Calculate the pOH:

* pOH = -log[OH-]

* pOH = -log(3.7 x 10^-5)

* pOH ≈ 4.43

2. Calculate the pH:

* pH + pOH = 14

* pH = 14 - pOH

* pH = 14 - 4.43

* pH ≈ 9.57

Therefore, the pH of the solution is approximately 9.57. This indicates that the solution is slightly basic.