How do you solve for critical value?

The critical value is a factor used to compute the margin of error, as shown in the equations below.

To find the critical value, follow these steps.
Compute alpha (α): α = 1 - (confidence level / 100)
Find the critical probability (p*): p* = 1 - α/2.
To express the critical value as a z-score, find the z-score having a cumulative probability equal to the critical probability (p*).